IGCSE/GCSE/O & A Level/IB/University Student Forum
Qualification => Subject Doubts => IGCSE/ GCSE => Sciences => Topic started by: mubashir on June 10, 2009, 11:47:43 am
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Since everybody races to start one of these topics :-*
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Hey can someone please solve this question and help me with the answer
i have attached the question below as a word document or else if u have de paper, it is question no 13 of november 1998
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also if anyone can please help me with question number 15 in november 1998
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don't have the paper
plzz upload it hre
i think the no 13 answer is D.....chlorine produced at the postitive side and sodium at negative
whats the answer in the markscheme
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the answer is d cause chlorine is produced at the anode ,,, and because it bleaches the indicator the colour becomes white near the anode.....
and at the cathode the alkali is formed which turns indicator blue....
hope i helped,,,,....
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the answer of 15 in nov 1998 is c....
because to make a reaction go slower.... we have to make the solid bigger...therefore less particles take part in the reaction...leading to less collision and a slower rate of rxn....
option 2 , is to make it less conc. this leads to less solute particles in da acid....therefore slower rate of rxn....
hope i helped...... :)
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the answer is d cause chlorine is produced at the anode ,,, and because it bleaches the indicator the colour becomes white near the anode.....
and at the cathode the alkali is formed which turns indicator blue....
hope i helped,,,,....
Hey but what alkali is formed at the cathode
shouldnt hydrogen be formed at the cathode??
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the answer of 15 in nov 1998 is c....
because to make a reaction go slower.... we have to make the solid bigger...therefore less particles take part in the reaction...leading to less collision and a slower rate of rxn....
option 2 , is to make it less conc. this leads to less solute particles in da acid....therefore slower rate of rxn....
hope i helped...... :)
ya Thanks a lot for de help. ive + repped u
however for this question de markscheme says A
isnt de markscheme wrong
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Can anyone upload the papers from below 1999?
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hey can anyne help me with this question please..
Its nov 07 ques 31... mark scheme says it should be B, i say its C..
can anyone tell me how?shouldnt it b C as oxygen is whats added to iron?
Thanks in advance ;D
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Yes, hydrogen is produced at the negative electrode, but if you look at the solution left: it's NaOH which is basic.
Na+ Cl-
H+ OH-
The ones coloured red are the ones that are produced at the electrodes, and what's left is Sodium hydroxide.
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Hi..
Can someone please tell me where i can find the old past papers like from the 90's?
Thanks :D
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They are torrented on www.freeetextbooks.com
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Hey people :)
PLease, does anyone have chemistry paper1 1999 till 2002 MARKING SCHEME??
I really need them guys , it is really important..
What is the use if I have the question papers and I don't have the marking scheme??
If anyone has, please say.... It will help us all.....
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Hey people :)
PLease, does anyone have chemistry paper1 1999 till 2002 MARKING SCHEME??
I really need them guys , it is really important..
What is the use if I have the question papers and I don't have the marking scheme??
If anyone has, please say.... It will help us all.....
I only have 2001-2002 Ms
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Yes, hydrogen is produced at the negative electrode, but if you look at the solution left: it's NaOH which is basic.
Na+ Cl-
H+ OH-
The ones coloured red are the ones that are produced at the electrodes, and what's left is Sodium hydroxide.
hey tammy thanks a lot for ur help
i had one more doubt about this
why is the sodium hyroxide formed at the cathode, shudnt it just form anywhere in the tube
y is it specifically formed at the cathode?????
nd shudnt de hydrogen formed at the cathode make the cathode area acidic>????
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NaOH form at the cathode cause the formula is :
2H2O+2e=h2+2OH-
THERFORE HYDROXIDE IONS FORM NEAR THE CATHODE .....
THIS HYDROXIDE IONS MAKE THE INDICATOR COLOUR GOES BLUE....
hope i helped.... :)
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NaOH form at the cathode cause the formula is :
2H2O+2e=h2+2OH-
THERFORE HYDROXIDE IONS FORM NEAR THE CATHODE .....
THIS HYDROXIDE IONS MAKE THE INDICATOR COLOUR GOES BLUE....
hope i helped.... :)
hey esso
but since de hydroxide ions are negatively charged shudnt dey be attracted to the positive electrode (anode)
nd how does water gain 2 electrons, where does it get dose 2 electrons from ????
im slightly confused
i understand dat oxidation taked place at the anode with clhorine ions losing electrons to form chlroine gas
and dat reduction takes place at cathode with hydrogen ions gaining electrons from de cathode to form hydrogen gas
den what happens to the remaining sodium ions nd hydroxide ions
how come they form near the cathode???
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since the hydroxide ions form near the cathode .... they attract the sodium ions and form at the cathode.....
.....dont have to know in detail though....
water gains electrons from the cathode ,,, therefore reduction takes place as u said .....
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since the hydroxide ions form near the cathode .... they attract the sodium ions and form at the cathode.....
.....dont have to know in detail though....
water gains electrons from the cathode ,,, therefore reduction takes place as u said .....
thanks a lot esso
+ rep for u
however dude i dont get it why do de hydroxide ions form near the cathode shudnt dey be attracted to de anode dats wat i dont undersatdn
i understand dat sodium ions are formed near de cathode since dey are attracted to the cathode as they are positive ions
nd dude y does water gain 2 electrons to form hydroxide
shudnt water naturally dissociate to form the hydrogen ions and hydroxide ions
because we have never been taught about water gaining 2 electrons from de cathode to form de hydroxde ions + hydrogen
we have been told dat water dissociates to produce hydrogen ions _ hydroxide ions
nd for hydroxide weve learnt that
4OH- = 2H20 + O2 + 4 electrons
can u please help as to why water gains two electrons from the cathode?????????/
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i really donot bt dat wat r teacher told us abt,....
let nid explain it to ya he will make it simplier as i am not good in explaining though......
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plz dont rite hope i helpd after each post with a childish smile -.-
its real degrading........
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every one has his own personal freedom..rite or i am wrong...
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-repped me rite...too many kids in this forum....
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i really donot bt dat wat r teacher told us abt,....
let nid explain it to ya he will make it simplier as i am not good in explaining though......
im she..*with pride*...lol...no time for jokin..
The answer is D for sure as chlorine bleaches damp litmus and alkali turns universal indicator blue
I'll explain the thing...give me two minutes. I'll frame my words well to make u understand
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but ur user name is nid rite... dats why i said nid...
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Let’s first consider the ions present
H+ OH-
Na+ Cl-
what exactly happens in the solution when electricity is passed through
The negative electrode(cathode) attracts the Hydrogen ions are attracted to it. They accept electrons to form hydrogen gas(which does not produce any change in the indicator)
At the positive electrode(anode), chloride ions are attracted. Here they lose two electrons to form chlorine gas. The chlorine bleaches the indicator.
The ions remaining form sodium hydroxide but the color change to blue is observed at the other electrode only because at the anode the indicator is bleached.
Ask again if u don't understand
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Let’s first consider the ions present
H+ OH-
Na+ Cl-
what exactly happens in the solution when electricity is passed through
The negative electrode(cathode) attracts the Hydrogen ions are attracted to it. They accept electrons to form hydrogen gas(which does not produce any change in the indicator)
At the positive electrode(anode), chloride ions are attracted. Here they lose two electrons to form chlorine gas. The chlorine bleaches the indicator.
The ions remaining form sodium hydroxide but the color change to blue is observed at the other electrode only because at the anode the indicator is bleached.
Ask again if u don't understand
oh allright got it thanx a lot nid. really nice of u to help
one more thing so de hydrogen formed at cathode doesnt affect de indicator becoz its as gas nd not as H+ ions,is dat de reason why de hydrogen gas has no effect on de indicator???
also so de sodium hydroxide is formed everywhere however it only affects the cathode region, because at the anode the litmus paper is bleached.. is dat rite
so if de litmus paper had not been bleached den even at de anode the litmus paper would have turned blue??
nd before chlroine turns damp blue litmus paper white it first turn the damn blue litmus paper red rite?? y is dat
nd one more question will sulphur dioxide gas react weith sodium hydroxide.. if yes what are the products
+ rep for u. Thanks a lot for ur help. hope im not wasting too much of ur time
which country r u from??
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can u please help me.. i kinda suck at chemisty but i heard this was a CORE paper is that true?
if it is where can i find CORE notes so i can study from them?
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can u please help me.. i kinda suck at chemisty but i heard this was a CORE paper is that true?
if it is where can i find CORE notes so i can study from them?
i don't think u can get notes specifically for the core syllabus. Ull have to co-relate the matter in ur text or guide with the core syllabus
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yah its core....just see the left hand column in the syllabus.....nd know abt dem...no need for the supplement things
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Let’s first consider the ions present
H+ OH-
Na+ Cl-
what exactly happens in the solution when electricity is passed through
The negative electrode(cathode) attracts the Hydrogen ions are attracted to it. They accept electrons to form hydrogen gas(which does not produce any change in the indicator)
At the positive electrode(anode), chloride ions are attracted. Here they lose two electrons to form chlorine gas. The chlorine bleaches the indicator.
The ions remaining form sodium hydroxide but the color change to blue is observed at the other electrode only because at the anode the indicator is bleached.
Ask again if u don't understand
oh allright got it thanx a lot nid. really nice of u to help
one more thing so de hydrogen formed at cathode doesnt affect de indicator becoz its as gas nd not as H+ ions,is dat de reason why de hydrogen gas has no effect on de indicator???
also so de sodium hydroxide is formed everywhere however it only affects the cathode region, because at the anode the litmus paper is bleached.. is dat rite
so if de litmus paper had not been bleached den even at de anode the litmus paper would have turned blue??
nd before chlroine turns damp blue litmus paper white it first turn the damn blue litmus paper red rite?? y is dat
nd one more question will sulphur dioxide gas react weith sodium hydroxide.. if yes what are the products
+ rep for u. Thanks a lot for ur help. hope im not wasting too much of ur time
which country r u from??
hydrogen gas simply does not affect the indicator. H+ions affect indiacators(since acids contain them)
if the indicator was not bleached it would have turned it blue throughout
It is in indicator in a solution(it's a universal indicator not litmus paper). *Chlorine does not turn litmus paper red anyways. The indicator is green in neutral solutions.
Sulphur dioxide will also react directly with bases such as sodium hydroxide solution. If sulphur dioxide is bubbled through sodium hydroxide solution, sodium sulphite solution is formed first followed by sodium hydrogensulphite solution when the sulphur dioxide is in excess. But y do u want to know this??
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and i forgot to mention.... I'm from India
....sorry for that robotic tone :D
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oh
thanx a lott
u seem to be a genius at chemistry
how do u know so much
u make me feel really dum :P
lol anywayz glad u know ur stuff really well
im from india as well
which city nd which school r u from??
guessing ur from bombay.. sound like dat
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nd one more question
which process can convert molecules to a new substance by removing hydrogen atoms
A displacement
B fermentation
C neutralisation
D oxidation
how do you solve this question
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nd one more question lol sorry
i have quite sum questions
for which metal are de use nd property correctly linked
B aluminium for food containers as it is light and resistant to corrosion
or D satinless steel for cutlery as it is cheap and strong
A and C are wrong so its between B and D
which on'e correct nid??
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Also
does anyone have the Chemisry Paper 1 for May and October 1993 since i cant seem to find dem anywhere
howcome dey are dere for physics nd biology but not for chem???
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nd one more question
which process can convert molecules to a new substance by removing hydrogen atoms
A displacement
B fermentation
C neutralisation
D oxidation
how do you solve this question
its neutralisation
and the answer to the next question which i am to lazy to quote is, B its aluminium
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nd one more question
which process can convert molecules to a new substance by removing hydrogen atoms
A displacement
B fermentation
C neutralisation
D oxidation
how do you solve this question
de ,arkscheme says its oxidation
nd for de next question de markscheme says it steel???????
dats y i am confused
nd y is it neutralisation anywayz
its neutralisation
and the answer to the next question which i am to lazy to quote is, B its aluminium
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nd one more question
which process can convert molecules to a new substance by removing hydrogen atoms
A displacement
B fermentation
C neutralisation
D oxidation
how do you solve this question
I find all of them except fermentation a possibility
Displacement- H2SO4+ 2 Na--> Na2SO4+H2
Neutralisation- NaOH+H2SO4-->Na2SO4+H2O
Oxidation- CH4+2O2-->CO2+2H2O
Can u post the paper it is from. i'll work on it and let u know...
and yup I'm from Bombay..MUMBAI
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can someone PLEASE help me...i need question papers for paper 1..i don't have any and i cant find them online either
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nd one more question
which process can convert molecules to a new substance by removing hydrogen atoms
A displacement
B fermentation
C neutralisation
D oxidation
how do you solve this question
hey i cant remeber de year it is from but this de exact question and according to the markscheme de answer is oxidation??
which school are u from in Mumbai??? ecole ?? podar?? ambani?? fazlani??
I find all of them except fermentation a possibility
Displacement- H2SO4+ 2 Na--> Na2SO4+H2
Neutralisation- NaOH+H2SO4-->Na2SO4+H2O
Oxidation- CH4+2O2-->CO2+2H2O
Can u post the paper it is from. i'll work on it and let u know...
and yup I'm from Bombay..MUMBAI
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GUYS, WHERE CAN I GET CHEMISTRY PAPER1 PAST PAPERS FROM 1993-2002?
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Can someone pls help to get markschemes for chemistry paper 1 : may/nov 2001
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Can someone pls help to get markschemes for chemistry paper 1 : may/nov 2001
Hey IGSTUDENT, look at page 1 bottom of this topic, and you'll find the MS!
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GUYS, COULD YOU PLEASE ATTACH CHEM P1 1993 UP TO 2002 or tell me how to get them?
THANX A TONNE!
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question paper or ms ??
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Both would be great^
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i have ms only ... ???
dont think tht will be off any help tho ....
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@john: Please check the question again cuz I feel it's incomplete.
Thanks
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HOW DO YOU GET 1993 TO 2002 PAPERS? CHEM P1 + MS?
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hey can anyne help me with this question please..
Its nov 07 ques 31... mark scheme says it should be B, i say its C..
can anyone tell me how?shouldnt it b C as oxygen is whats added to iron?
Thanks in advance ;D
dude it cannot be C bcoz carbon is only used to make only industrial steel n they r asking abt different types of steel which means more than one type so the answer is chromium n nickel because they r transition elements the answer is B
ppl plz correct me if im wrong
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maaaaan...check the periodic table! Carbon isnt in C (group 6)
beside in B(transition metals)...u have nickel and chromium..used to make stainless steel!
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HOW DO YOU GET 1993 TO 2002 PAPERS? CHEM P1 + MS?
give me ur email.....i ll send it across......Q80BOY had given dem in nother topic ;)...thnkz Q80
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@john: Please check the question again cuz I feel it's incomplete.
Thanks
hey no nid the question is complete
even i though its weird but dats all de question says
de markscheme says its oxidation
i guesss it cant be neutralisation cause in dat hydrogen ions are involved not atoms nd hence it must be oxidation as atoms are involved in oxidation
also ions take part in displacement so it cant be dat
i guess??
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nd one more question
which process can convert molecules to a new substance by removing hydrogen atoms
A displacement
B fermentation
C neutralisation
D oxidation
how do you solve this question
john it is oxidation By the way it is not der 4r us it cums in O-levels loss of hydrogen is oxidation
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OK so I have a few questions
1)hydrogen can form both ionic and covalent compounds
with which element will hydorgen form an ionic compound?
a-carbon
b-chlorine
c-nitrogen
d-sodium
2)CuSO4 (aq) is electrolysed using Cu electrodes
what observations will be made?
at anode at cathode electrolyte
a- anode dissolves pink solid forms blue color fades
b- anode dissolves pink solid forms no change
c- colourless gas forms colourless gas forms no change
d- colourless gas forms pink solid forms blue color fades
3) The carbonate of metal x is a white solid
it decomposes when heated to form co2 gas and a yellow solid oxide
what is metal x
a-copper
b-iron
c-lead
d-sodium
Can somebody please answer them with explaination
Thanks
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1) SODIUM SINCE ITS DA ONLY METAL
2) "D" SINCE hydroxide is colourless gas...copper pink solid!!
3)can u post the paper...i remeba doin' it buh cnt give xact explanation unless sure of answer!
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OK so I have a few questions
1)hydrogen can form both ionic and covalent compounds
with which element will hydorgen form an ionic compound?
a-carbon
b-chlorine
c-nitrogen
d-sodium
2)CuSO4 (aq) is electrolysed using Cu electrodes
what observations will be made?
at anode at cathode electrolyte
a- anode dissolves pink solid forms blue color fades
b- anode dissolves pink solid forms no change
c- colourless gas forms colourless gas forms no change
d- colourless gas forms pink solid forms blue color fades
3) The carbonate of metal x is a white solid
it decomposes when heated to form co2 gas and a yellow solid oxide
what is metal x
a-copper
b-iron
c-lead
d-sodium
Can somebody please answer them with explaination
Thanks
its 1 d, 2B n 3a
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1=d
2=b
3=i doubt da q
yellow oxide???
r u sure that its in question
yellow!!!
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ok itz defi sodium 4 da 1st
but guyz 4 da 2nd...itz 'b'.....itz using copper electrodes wich r active electrodes.......im sure u hv don't da purification of copper using electrolysis...itz da same thng
n 3rd.....im not sure but i thnk itz sodium bcuz itz an alkali wich forms white compounds....
plz nid or any1...correct me if im wrong.....thnku :)
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ok itz defi sodium 4 da 1st
but guyz 4 da 2nd...itz 'b'.....itz using copper electrodes wich r active electrodes.......im sure u hv don't da purification of copper using electrolysis...itz da same thng
n 3rd.....im not sure but i thnk itz sodium bcuz itz an alkali wich forms white compounds....
plz nid or any1...correct me if im wrong.....thnku :)
yeah....priceless
thats wat i said...2 is b
cuz cu electrodes r being used!!!!
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OK so I have a few questions
1)hydrogen can form both ionic and covalent compounds
with which element will hydorgen form an ionic compound?
a-carbon
b-chlorine
c-nitrogen
d-sodium
2)CuSO4 (aq) is electrolysed using Cu electrodes
what observations will be made?
at anode at cathode electrolyte
a- anode dissolves pink solid forms blue color fades
b- anode dissolves pink solid forms no change
c- colourless gas forms colourless gas forms no change
d- colourless gas forms pink solid forms blue color fades
3) The carbonate of metal x is a white solid
it decomposes when heated to form co2 gas and a yellow solid oxide
what is metal x
a-copper
b-iron
c-lead
d-sodium
Can somebody please answer them with explaination
Thanks
Last one has to be iron.
Copper oxide is black.
Sodium carbonate doesn't decompose.
Iron oxide is yellow.
Lead oxide is dark brown-black
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ok itz defi sodium 4 da 1st
but guyz 4 da 2nd...itz 'b'.....itz using copper electrodes wich r active electrodes.......im sure u hv don't da purification of copper using electrolysis...itz da same thng
n 3rd.....im not sure but i thnk itz sodium bcuz itz an alkali wich forms white compounds....
plz nid or any1...correct me if im wrong.....thnku :)
IT CANT BE B for da second one because the overall concentration of cu2+ ions remain the saME its jus the copper frm the anode tht gets coated on the cathode
n abt 3 it culd be copper
it cannot be sodium because carbonates of highly reactive metals are quite stable n do not decompose on heating except lithium i think n copper oxide i think is yellow sort of
plz correct me if im wrong
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yea srry copper oxide is black
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yea srry copper oxide is black
yep..but da 3rd one i doubt da question.....none can be yellow....
By the way....he is not replying......wrs he...cocky..
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yea srry copper oxide is black
yep..but da 3rd one i doubt da question.....none can be yellow....
By the way....he is not replying......wrs he...cocky..
Umm, iron (III) oxide is yellow.
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xactly madee.....so dats y ders no change in da electrolyte....so it is 'b'...
n thnkz though madee n i-insane...i 4got abt dat sodium CO3 duznt decompose......but is iron carbonate white?
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no.its brown
i guess...........
i havent been to the lab since 2 years.. .......!!!!
my cheap school [sighs]
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hey guyz will somebody help me in this question number 25 november 06.....
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no.its brown
i guess...........
i havent been to the lab since 2 years.. .......!!!!
my cheap school [sighs]
lol...cmon mr bombastic..... :)
but nw im evn more confused.....wats da answer den ???......wers cockyx?
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xactly madee.....so dats y ders no change in da electrolyte....so it is 'b'...
n thnkz though madee n i-insane...i 4got abt dat sodium CO3 duznt decompose......but is iron carbonate white?
No kidding, but I've never even heard of zinc carbonate :P
But, sodium carbonate doesn't decomposes, lead oxide is black, copper oxide is black, iron oxide is yellow..so iron is the only thing possible. Even if you consider sodium, sodium oxide is white.
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1) SODIUM SINCE ITS DA ONLY METAL
2) "D" SINCE hydroxide is colourless gas...copper pink solid!!
3)can u post the paper...i remeba doin' it buh cnt give xact explanation unless sure of answer!
you ppl sure
i think it shud b chlorine cos hcl is an ionic compound in liquid
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yes shafiq...im pretty sure abt sodium.....ionic compounds is da bonding b/w a metal n a non-metal....
n i-insane.....lol....i guess itz iron den but not sure though......thnkz though...all da best :)
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yah but nah sounds wrong 0_0
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hey guyz will somebody help me in this question number 25 november 06.....
Copper is low in the reactivity series, and doesn't react with acids or steam/cold water.
Magnesium reacts with steam and acids but not with cold water unless crushed.
Calcium reacts with all, acids, steam and cold water.
Thus, only calcium and magnesium react to form hydrogen.
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cmon....lol....sounds wrong?....just go wid ur facts n knowledge ;) :D
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GUYS, WHERE CAN I GET CHEMISTRY PAPER1 PAST PAPERS FROM 1993-2002?
did u get the markschemes for them? if yes from where? i rlyy need them!
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in da last question of yellow oxide..
there should be another option
E."NONE OF THE ABLOVE"
and i would choose E...lolzzzzzzzzz
wr r u cocky......... :(
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yes shafiq...im pretty sure abt sodium.....ionic compounds is da bonding b/w a metal n a non-metal....
n i-insane.....lol....i guess itz iron den but not sure though......thnkz though...all da best :)
All the best to you too!
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lol....mr bombastic....i thnk i wud hv don't da same thng...rite behind ya :P :D
n Take care guyz....all da best 2 u all ;)
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1) SODIUM SINCE ITS DA ONLY METAL
2) "D" SINCE hydroxide is colourless gas...copper pink solid!!
3)can u post the paper...i remeba doin' it buh cnt give xact explanation unless sure of answer!
you ppl sure
i think it shud b chlorine cos hcl is an ionic compound in liquid
dude no offence but r u sure u r appearin for a chem paper 2morrow because it doesnt luk like how can hcl be ionic
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GUYS, WHERE CAN I GET CHEMISTRY PAPER1 PAST PAPERS FROM 1993-2002?
did u get the markschemes for them? if yes from where? i rlyy need them!
check your email in half an hour
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lol im sure im appearing lol
im great wid organic and most of da hard stuff
bt i suck at acids bases and da ionic stuff ><
bt hcl is ionic
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lol im sure im appearing lol
im great wid organic and most of da hard stuff
bt i suck at acids bases and da ionic stuff ><
bt hcl is ionic
ionic bonds are formed onli between metals n non metals n HCL is not ionic bcoz neither is hydrogen a metal n nor is chlorine
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okay but hcl does dissosciate into ions
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but you guys are ryt sodium is da answer >< anyways i shud study ciao ppl
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okay but hcl does dissosciate into ions
i didnt get u how is tht suppose to make it an ionic compounds all strong acids disassocite completely in to der ions tht means all acids are ionic compounds
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All i remember is, we once, in paper 3, had to draw a sodium hydride structure, with formula NaH. So that should be ionic then.
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All i remember is, we once, in paper 3, had to draw a sodium hydride structure, with formula NaH. So that should be ionic then.
yes it is
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PPL.......Lead Oxide is yellow!!
if it was Iron Oxide then it wont be yellow.......it would be green or reddish brown depend on the valency of iron
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I stand corrected.
Indeed, lead (II) oxide is yellow and lead (I) oxide is dark brown. And lead (II) carbonate is, undoubtedly, white. Thus answer has to be lead.
Thank you Triple_A.
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ok itz defi sodium 4 da 1st
but guyz 4 da 2nd...itz 'b'.....itz using copper electrodes wich r active electrodes.......im sure u hv don't da purification of copper using electrolysis...itz da same thng
n 3rd.....im not sure but i thnk itz sodium bcuz itz an alkali wich forms white compounds....
plz nid or any1...correct me if im wrong.....thnku
sry ma bad i didnt read copper electordes in da question :-[
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hey guys id appreciate some help.may june 03 q21
water is added to dilute H2SO4 of pH4.What is the resulting pH?
the answer is 6,but why?i know it has something to do with the hydroxide or hydrogen ions in water which change its pH....
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PPL.......Lead Oxide is yellow!!
if it was Iron Oxide then it wont be yellow.......it would be green or reddish brown depend on the valency of iron
r u sure der was sum1 astar sumthin he said he is a private tutor i so want him to answer this n By the way whr r da big brains those ppl nid n every1
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hey guys id appreciate some help.may june 03 q21
water is added to dilute H2SO4 of pH4.What is the resulting pH?
the answer is 6,but why?i know it has something to do with the hydroxide or hydrogen ions in water which change its pH....
Water has a pH of 7, so when it is added to a pH4 substance, it will try to bring the pH of the substance to 7. Since 8 is above 7, it is wrong. The pH can't remain same, and neither can it become further acidic, so it has to be the one that is close to 7, or slightly less than it. That is 6.
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hey guys id appreciate some help.may june 03 q21
water is added to dilute H2SO4 of pH4.What is the resulting pH?
the answer is 6,but why?i know it has something to do with the hydroxide or hydrogen ions in water which change its pH....
its jus tht it bcums dilute so the pH lowers i think so
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hey guys id appreciate some help.may june 03 q21
water is added to dilute H2SO4 of pH4.What is the resulting pH?
the answer is 6,but why?i know it has something to do with the hydroxide or hydrogen ions in water which change its pH....
it has nothing to do with hydroxide..
when u add water it becomes diluted so its ph increases...
hope u got it now... :)
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hey guys id appreciate some help.may june 03 q21
water is added to dilute H2SO4 of pH4.What is the resulting pH?
the answer is 6,but why?i know it has something to do with the hydroxide or hydrogen ions in water which change its pH....
LOW PH+high PH=neutral
high ph+ high ph= alkaline
low ph+ low ph= acidic
in this case a low ph and a neutral would give u weak acidic only
further xplanation of the results of neutralisation i think is nt needed!
NOW I GOT A QUESTION: NOV08 Q13: y is it B not A?????
-
i need help in this question <
Three reactions used in the manufacture of sulphuric acid are shown.
1 S + O2 ? SO2
2 2SO2 + O2 ? 2SO3
3 SO3 + H2O ? H2SO4
Which of these reactions are redox reactions?
A 1 only
B 3 only
C 1 and 2 only
D 2 and 3 only
-
thanks for your help everyone.
to answer your Q,sweetest angel,its because if it were in solution,the hydrogen would be liberated in preference to lead.
-
Hey! Can someone tell me why q4 in november 08 is A? Ionic compounds are soluble in ethanol and water
And also november 2007 no. 21, shouldn' it form a blue percepitate??
-
hey guys id appreciate some help.may june 03 q21
water is added to dilute H2SO4 of pH4.What is the resulting pH?
the answer is 6,but why?i know it has something to do with the hydroxide or hydrogen ions in water which change its pH....
LOW PH+high PH=neutral
high ph+ high ph= alkaline
low ph+ low ph= acidic
in this case a low ph and a neutral would give u weak acidic only
further xplanation of the results of neutralisation i think is nt needed!
NOW I GOT A QUESTION: NOV08 Q13: y is it B not A?????
they asked u abt the metal lead's bromide so it has to be molten
-
i need help in this question <
Three reactions used in the manufacture of sulphuric acid are shown.
1 S + O2 ? SO2
2 2SO2 + O2 ? 2SO3
3 SO3 + H2O ? H2SO4
Which of these reactions are redox reactions?
A 1 only
B 3 only
C 1 and 2 only
D 2 and 3 only
its 1 n 2 i suppose
-
thanks for your help everyone.
to answer your Q,sweetest angel,its because if it were in solution,the hydrogen would be liberated in preference to lead.
i thought dat 2 but lead is higher in reactivity series than hydrogen!! =s
-
i need help in this question <
Three reactions used in the manufacture of sulphuric acid are shown.
1 S + O2 ? SO2
2 2SO2 + O2 ? 2SO3
3 SO3 + H2O ? H2SO4
Which of these reactions are redox reactions?
A 1 only
B 3 only
C 1 and 2 only
D 2 and 3 only
2 and 3?
i saw this question be4...can u tell me which year please?
-
Hey! Can someone tell me why q4 in november 08 is A? Ionic compounds are soluble in ethanol and water
And also november 2007 no. 21, shouldn' it form a blue percepitate??
ionic compounds dissolve in water n covalent dont n covalent dissolve in organic solvents n ionic dont so with either methods dey can be separated the undissolved compound is left as reidue
-
the ans is actually c, 1and2
-
hey when you polymerise an an alkene,e.g. ethene,does it become polyethEne or polyethAne?
-
Hey! Can someone tell me why q4 in november 08 is A? Ionic compounds are soluble in ethanol and water
And also november 2007 no. 21, shouldn' it form a blue percepitate??
ionic compounds dissolve in water n covalent dont n covalent dissolve in organic solvents n ionic dont so with either methods dey can be separated the undissolved compound is left as reidue
reagent aq BaCl is wrong
@mizuki........polyethene
-
oct05 que.32
may06 que.19
oct06 que.5
can any1 plzzzzzz xplain ans. 2 dese que"s
-
hi
does anyi know why the ans to q29, 2004jun is C
-
u guys..
help me..
ppr 1,june04, 32..
why would the screws be the aluminium?..
aluminium would never corrode..because it forms oxide layer?
-
i need help in this question <
Three reactions used in the manufacture of sulphuric acid are shown.
1 S + O2 ? SO2
2 2SO2 + O2 ? 2SO3
3 SO3 + H2O ? H2SO4
Which of these reactions are redox reactions?
A 1 only
B 3 only
C 1 and 2 only
D 2 and 3 only
2 and 3?
i saw this question be4...can u tell me which year please?
its in may june 2007 .... but can u explain it ????
-
oct05 que.32
may06 que.19
oct06 que.5
can any1 plzzzzzz xplain ans. 2 dese que"s
for the first one its lime bcoz lime is calciumcarbonate bcoz it consists of calcium which is highly reactive n will not decompose
for the second metals below hydrogen will not react with acids n copper is below hydrogen all the others will react
n for the last one its C
the 35 n 37 are isotopes of chlorine n the 18 is argon chk the periodic table
-
hi
does anyi know why the ans to q29, 2004jun is C
take the percentage of o2 to be 21% now
21/100*x=30
solve u will get 142 sumthin so the nearest value is 150 so it is c
-
Hey! Can someone tell me why q4 in november 08 is A? Ionic compounds are soluble in ethanol and water
And also november 2007 no. 21, shouldn' it form a blue percepitate??
ionic compounds dissolve in water n covalent dont n covalent dissolve in organic solvents n ionic dont so with either methods dey can be separated the undissolved compound is left as reidue
reagent aq BaCl is wrong
@mizuki........polyethene
Thanks! XD
Why is it wrong? It will form a blue percepitate of copper chloride right?
-
i need help in this question <
Three reactions used in the manufacture of sulphuric acid are shown.
1 S + O2 ? SO2
2 2SO2 + O2 ? 2SO3
3 SO3 + H2O ? H2SO4
Which of these reactions are redox reactions?
A 1 only
B 3 only
C 1 and 2 only
D 2 and 3 only
2 and 3?
i saw this question be4...can u tell me which year please?
may/june 2007 :)
-
u guys..
help me..
ppr 1,june04, 32..
why would the screws be the aluminium?..
aluminium would never corrode..because it forms oxide layer?
here dey r testing for preferential discharge thing aluminium is more reactive hence it will loose electrons n will not let steel to do so
-
u guys..
help me..
ppr 1,june04, 32..
why would the screws be the aluminium?..
aluminium would never corrode..because it forms oxide layer?
here dey r testing for preferential discharge thing aluminium is more reactive hence it will loose electrons n will not let steel to do so
oh...really?..
i alwys keep rembr that aluminium doesn't corrode..
nways..thanks..+rep
-
the answer is ''A'',because,the number of molecules for successful collisions are less and also if the acid is less concentrated,the number of molecules in the same volume present,are less,and hence,less number of successful collisions in the same period of time,and hence,a slower reaction rate.
-
the answer is ''A'',because,the number of molecules for successful collisions are less and also if the acid is less concentrated,the number of molecules in the same volume present,are less,and hence,less number of successful collisions in the same period of time,and hence,a slower reaction rate.
[/quote
this is an ans to which que
-
ppl i wud b verry gratful if any1 cud tell me whether aluminium oxide is soluble in water????? ???
-
ppl i wud b verry gratful if any1 cud tell me whether aluminium oxide is soluble in water????? ???
no it is not soluble
-
ppl i wud b verry gratful if any1 cud tell me whether aluminium oxide is soluble in water????? ???
no it is not soluble
aluminium is soluble!!!
-
hmmm sooo is it soluble or insoluble???
-
hmmm sooo is it soluble or insoluble???
Hydrated aluminium oxide is readily soluble in acids or alkalies
-
It's not soluble!!!
I know I saw the question in one of the old pastpapers and asked my teacher and he said it's insoluble ;D
-
guys aluminum hydrous oxide is soluble in acids but not in water
-
Guuuyysss can someone please help me with november 2007 no. 21, shouldnt' it form a blue percepitate??
-
Guuuyysss can someone please help me with november 2007 no. 21, shouldnt' it form a blue percepitate??
only cu sulfate is blue not all compounds of copper are blue
-
Guuuyysss can someone please help me with november 2007 no. 21, shouldnt' it form a blue percepitate??
only cu sulfate is blue not all compounds of copper are blue
did u get it now
-
The answer is C
-
The answer is C
heyy, please help....
O/N 2007, paper 1, Q 11
-
An aqueous solution contains barium iodide.
It is possible to obtain a solution that contains Ba2+(aq) but no I–(aq) by adding ……1…… until no
more ……2…… precipitate forms.
Which words correctly complete gaps 1 and 2?
1 2
A aqueous lead(II) nitrate white
B aqueous lead(II) nitrate yellow
C dilute sulphuric acid white
D dilute sulphuric acid yellow
help please...need an explanation..
-
is a burette is used for a very accurate amount compared to a pipette?
-
this is from may 05, if anyone has solved it, pls help me.
for question 16, the answer is D
y cnt it b C? pls help, thanks in advance
-
burette!!!!!!
i did in 1 of da past pprs
-
pippete is to measure fixed volumes...like 25 cm3 or 30 cm3
but burrete is vry accurate ,when compared with m.cylinder,and its used to measure varying volumes,like 35.5 or 47.2
hope i helped...
-
An aqueous solution contains barium iodide.
It is possible to obtain a solution that contains Ba2+(aq) but no I–(aq) by adding ……1…… until no
more ……2…… precipitate forms.
Which words correctly complete gaps 1 and 2?
1 2
A aqueous lead(II) nitrate white
B aqueous lead(II) nitrate yellow
C dilute sulphuric acid white
D dilute sulphuric acid yellow
help please...need an explanation..
U omit C and D first cuz if u want barium ions in the solution that reacting it with acid gives sulphate which is not soluble.
Since u want barium ions to be in the solution, u want iodide to precipitate so that it can be filtered. So u add Lead nitrate and this will react with barium iodide to give barium nitrate and lead iodide(which is yellow). lead iodide can be filtered as it is insoluble and will precipitate. the solution will contain no iodide ions.
I hope it's clear... :-\
-
this is from may 05, if anyone has solved it, pls help me.
for question 16, the answer is D
y cnt it b C? pls help, thanks in advance
For 3, there would be no loss in mass, as any gas produced would remain inside the conical flask, and not be able to excape through the stopper.
-
nd one more question
which process can convert molecules to a new substance by removing hydrogen atoms
A displacement
B fermentation
C neutralisation
D oxidation
how do you solve this question
john it is oxidation By the way it is not der 4r us it cums in O-levels loss of hydrogen is oxidation
Just didn't strike my mind...thanx for reminding and moreover for helping john :)
-
An aqueous solution contains barium iodide.
It is possible to obtain a solution that contains Ba2+(aq) but no I–(aq) by adding ……1…… until no
more ……2…… precipitate forms.
Which words correctly complete gaps 1 and 2?
1 2
A aqueous lead(II) nitrate white
B aqueous lead(II) nitrate yellow
C dilute sulphuric acid white
D dilute sulphuric acid yellow
help please...need an explanation..
U omit C and D first cuz if u want barium ions in the solution that reacting it with acid gives sulphate which is not soluble.
Since u want barium ions to be in the solution, u want iodide to precipitate so that it can be filtered. So u add Lead nitrate and this will react with barium iodide to give barium nitrate and lead iodide(which is yellow). lead iodide can be filtered as it is insoluble and will precipitate. the solution will contain no iodide ions.
I hope it's clear... :-\
ya crystal clear...Thanks for d help...
-
Guys please help with this,...
When lithium reacts with water, if forms lithium oxide + hydrogen OR it forms lithium hydroxide + hydrogen????
And which metals react with water to form metal oxide + hydrogen and which ones react with water to form metal hydroxide + hydrogen???
Help please???
-
Please help.....O/N 2007, paper 1, Q11
please explain, thanks in advance...
-
this is from may 05, if anyone has solved it, pls help me.
for question 16, the answer is D
y cnt it b C? pls help, thanks in advance
For 3, there would be no loss in mass, as any gas produced would remain inside the conical flask, and not be able to excape through the stopper.
yea bt if it dusnt escape, u can still use it cuz the mass will increase as gas is produced and wont escape. da mass will increase
rite?
-
its neutrilisation rite....cause hydrogen is removed from acids when reacting with bases
-
Guys please help with this,...
When lithium reacts with water, if forms lithium oxide + hydrogen OR it forms lithium hydroxide + hydrogen????
And which metals react with water to form metal oxide + hydrogen and which ones react with water to form metal hydroxide + hydrogen???
Help please???
Lithium is a group 1 metal so it forms hydroxide and hydrogen
Group 2 metals react to form metal oxide and hydrogen(but magnesium reacts with steam to give hydroxide
Metals below hydrogen in reactivity do not form either.
-
this is from may 05, if anyone has solved it, pls help me.
for question 16, the answer is D
y cnt it b C? pls help, thanks in advance
u cannot take 3 bcoz a stopper will not allow the gas to escape n the two methods loss of mass wid time n amount of gas collected by the passage time are used in 2 n 4
-
this is from may 05, if anyone has solved it, pls help me.
for question 16, the answer is D
y cnt it b C? pls help, thanks in advance
For 3, there would be no loss in mass, as any gas produced would remain inside the conical flask, and not be able to excape through the stopper.
yea bt if it dusnt escape, u can still use it cuz the mass will increase as gas is produced and wont escape. da mass will increase
rite?
Umm no, conservation of mass = mass of products is always equal to mass of reactants. So, to show the rate of reaction, a decrease in mass must occur.
-
nd one more question
which process can convert molecules to a new substance by removing hydrogen atoms
A displacement
B fermentation
C neutralisation
D oxidation
how do you solve this question
john it is oxidation By the way it is not der 4r us it cums in O-levels loss of hydrogen is oxidation
from which paper is this question ???
-
this is from may 05, if anyone has solved it, pls help me.
for question 16, the answer is D
y cnt it b C? pls help, thanks in advance
For 3, there would be no loss in mass, as any gas produced would remain inside the conical flask, and not be able to excape through the stopper.
yea bt if it dusnt escape, u can still use it cuz the mass will increase as gas is produced and wont escape. da mass will increase
rite?
Umm no, conservation of mass = mass of products is always equal to mass of reactants. So, to show the rate of reaction, a decrease in mass must occur.
ok so always a decrease in mass.
thanks alot :) +rep
-
and guys doesnt sodium oxide hav a pH above 7 (metal oxide)
den how cum the answer in nov 05, question 17 is C ???
-
and guys doesnt sodium oxide hav a pH above 7 (metal oxide)
den how cum the answer in nov 05, question 17 is C ???
it bcums dilute pH is lowered
-
and guys doesnt sodium oxide hav a pH above 7 (metal oxide)
den how cum the answer in nov 05, question 17 is C ???
Read the question correctly. Sodium oxide, when in solution it forms OH-ions which give the pH for the solution and changes pH of water(7) to 12
Hence C
-
and guys doesnt sodium oxide hav a pH above 7 (metal oxide)
den how cum the answer in nov 05, question 17 is C ???
it bcums dilute pH is lowered
but pH has nothing to do wid water and dilute Sad
plus its a metal oxide, the pH has to be above 7.
-
and guys doesnt sodium oxide hav a pH above 7 (metal oxide)
den how cum the answer in nov 05, question 17 is C ???
it bcums dilute pH is lowered
but pH has nothing to do wid water and dilute Sad
plus its a metal oxide, the pH has to be above 7.
Tell me what pH of water is
-
and guys doesnt sodium oxide hav a pH above 7 (metal oxide)
den how cum the answer in nov 05, question 17 is C ???
Read the question correctly. Sodium oxide, when in solution it forms OH-ions which give the pH for the solution and changes pH of water(7) to 12
Hence C
oh so da sodium oxide is added to the water. omg, stupid me
thanks nid :) as always, i say thanks to u, haha
+rep
-
and guys doesnt sodium oxide hav a pH above 7 (metal oxide)
den how cum the answer in nov 05, question 17 is C ???
Read the question correctly. Sodium oxide, when in solution it forms OH-ions which give the pH for the solution and changes pH of water(7) to 12
Hence C
yea srry i rote it according to tht sodium i didnt read the que properly
-
can sum1 explain this que plz
Please help.....O/N 2007, paper 1, Q11
-
Please help.....O/N 2007, paper 1, Q11
please explain, thanks in advance...
For this, you have to form a balanced equation for the combustion of each of them. The one that forms a balanced equation with 8O2 is the correct one.
The answer is B, because...
C6H9OH + 8O2 -----> 6CO2 + 5H2O
You can form a balanced equation with B, so B is the answer
-
Please help.....O/N 2007, paper 1, Q11
please explain, thanks in advance...
For this, you have to form a balanced equation for the combustion of each of them. The one that forms a balanced equation with 8O2 is the correct one.
The answer is B, because...
C6H9OH + 8O2 -----> 6CO2 + 5H2O
You can form a balanced equation with B, so B is the answer
Thanks but i think der is sumtin more to it
-
Please help.....O/N 2007, paper 1, Q11
please explain, thanks in advance...
For this, you have to form a balanced equation for the combustion of each of them. The one that forms a balanced equation with 8O2 is the correct one.
The answer is B, because...
C6H9OH + 8O2 -----> 6CO2 + 5H2O
You can form a balanced equation with B, so B is the answer
Thanks but i think der is sumtin more to it
Hmm, like?
The main thing is that, only one molecule of each organic compound is to be used in your equation.
-
Please help.....O/N 2007, paper 1, Q11
please explain, thanks in advance...
For this, you have to form a balanced equation for the combustion of each of them. The one that forms a balanced equation with 8O2 is the correct one.
The answer is B, because...
C6H9OH + 8O2 -----> 6CO2 + 5H2O
You can form a balanced equation with B, so B is the answer
Thanks but i think der is sumtin more to it
Hmm, like?
no i think its f9 may be dey want us to actually sit n balance
anywayz Thanks
-
Please help.....O/N 2007, paper 1, Q11
please explain, thanks in advance...
For this, you have to form a balanced equation for the combustion of each of them. The one that forms a balanced equation with 8O2 is the correct one.
The answer is B, because...
C6H9OH + 8O2 -----> 6CO2 + 5H2O
You can form a balanced equation with B, so B is the answer
Thanks but i think der is sumtin more to it
Hmm, like?
no i think its f9 may be dey want us to actually sit n balance
anywayz Thanks
No problem at all!
-
and guys doesnt sodium oxide hav a pH above 7 (metal oxide)
den how cum the answer in nov 05, question 17 is C ???
Read the question correctly. Sodium oxide, when in solution it forms OH-ions which give the pH for the solution and changes pH of water(7) to 12
Hence C
yea srry i rote it according to tht sodium i didnt read the que properly
its K :)
-
hey guys ...
ive got a question from nov 2001
Page 4, Question 6 ...
Neon has 10 e- and Sodium has 11 e- which makes the answer C, but the mark scheme says its D ...
help !!
-
hey guys ...
ive got a question from nov 2001
Page 4, Question 6 ...
Neon has 10 e- and Sodium has 11 e- which makes the answer C, but the mark scheme says its D ...
help !!
dude it is sodium ion tht means it has already lost one electron this makes it 10 electrons
-
hey guys ...
ive got a question from nov 2001
Page 4, Question 6 ...
Neon has 10 e- and Sodium has 11 e- which makes the answer C, but the mark scheme says its D ...
help !!
it has to be D cuz sodium atom has10, cuz Na+ and loses one electron. so 8 on the outer and none on the last.
neon has to hav complete shells cuz its gr.8
hope i helped
-
Its D since sodium ion is asked.
-
ooooh, i didnt read the ion, i thought it was atom :-[
silly me !! :P
thanks for all the help guys ;)
-
guys i need help wid May 06, no. 29
y is it D? doesnt chrome plated keyring, rust?
-
guys i need help wid May 06, no. 29
y is it D? doesnt chrome plated keyring, rust?
No, that's the whole point, chromium is resistant to corrosion. That is why stainless steel (which contains chromium) is used to plate cutlery.
-
guys i need help wid May 06, no. 29
y is it D? doesnt chrome plated keyring, rust?
No, that's the whole point, chromium is resistant to corrosion. That is why stainless steel (which contains chromium) is used to plate cutlery.
oh ok so its nthng to do wid da experiment
thanks :) +rep
-
ugh the karma isnt leting me rep u, sry :(
-
guys i need help wid May 06, no. 29
y is it D? doesnt chrome plated keyring, rust?
ya chromium is resistant to corrosion n the brass scre will not rust because thte test tube contains nitrogen
-
the OH in the COOH of a carboxilyic acid reacts wid NaOH?
-
the OH in the COOH of a carboxilyic acid reacts wid NaOH?
Yes, it does! :)
-
the OH in the COOH of a carboxilyic acid reacts wid NaOH?
wht r u tryin to say i culdnt get u
-
the OH in the COOH of a carboxilyic acid reacts wid NaOH?
wht r u tryin to say i culdnt get u
its a question from may 06 paper
-
the OH in the COOH of a carboxilyic acid reacts wid NaOH?
Yes, it does! :)
oh okie :)
can anyone help me wid question 11 from Nov 06 paper?
i dont get the question. wont the products jus be chlorine in the anode and Hydrogen in the cathode ???
and sry for lota questions ppl :(
-
the OH in the COOH of a carboxilyic acid reacts wid NaOH?
wht r u tryin to say i culdnt get u
its a question from may 06 paper
it isque no 35 ryt
no it cannot
how can u have an oh reacting wid another base only da cooh can react the answer is C
-
the OH in the COOH of a carboxilyic acid reacts wid NaOH?
Yes, it does! :)
oh okie :)
can anyone help me wid question 11 from Nov 06 paper?
i dont get the question. wont the products jus be chlorine in the anode and Hydrogen in the cathode ???
and sry for lota questions ppl :(
wen cl is liberated wht is left bck water n the sodium so all ttht forms sodium hydroxide
-
hm neone has 2002 n 2001 qp along wth ms fr bth oct n nov
plz post
-
cn anyone plzzzz xplain da answer 2 chem ppr1 que 20 oct07????
thanx
-
cn anyone plzzzz xplain da answer 2 chem ppr1 que 20 oct07????
thanx
Both, carbon and calcium react with oxygen in the air. Carbon dioxide forms in the case of carbon, which escapes as a gas, so mass decreases. Calcium oxide formed in the case of calcium, which is a solid, and so mass increases.
-
cn anyone help me wid question 9 from oct 07?
-
cn anyone help me wid question 9 from oct 07?
Electrolytes are either molten or aqueous. Since water is already there and you have to add something into it, the electrolyte is supposed to be aqueous. For the electrolyte to be aqueous, a soluble salt has to be added to water. That soluble salt is potassium sulfate (D)
-
cn anyone help me wid question 9 from oct 07?
Electrolytes are either molten or aqueous. Since water is already there and you have to add something into it, the electrolyte is supposed to be aqueous. For the electrolyte to be aqueous, a soluble salt has to be added to water. That soluble salt is potassium sulfate (D)
thanks alot :)
-
cn anyone plzzzz xplain da answer 2 chem ppr1 que 20 oct07????
thanx
Both, carbon and calcium react with oxygen in the air. Carbon dioxide forms in the case of carbon, which escapes as a gas, so mass decreases. Calcium oxide formed in the case of calcium, which is a solid, and so mass increases.
i had the same doubt, thanks once agn.
-
No problem! :)
-
will someone explain to me question 11 november07
-
Can someone help me for ques. 36 in OCT/NOV 1997?
-
Can someone help me for ques. 36 in OCT/NOV 1997?
can u send me the paper i dont have it or atlst write the comp que
-
11 For complete combustion, one molecule of an organic compound needs 8 molecules of oxygen.
What could the formula of this compound be?
A C5H11OH
B C6H9OH
C C6H11OH
D C6H12
B is the only one that balances with 8O2
C6H9OH+8O2>5HO2+6CO2
-
will someone explain to me question 11 november07
hey lsn d ans is b
d eq is like 1mol of org. + 8mol of 02
so c6h90h+ 8o2= 6co2+ 5h20
-
Can any one give me any tips to do with chemistry, its the hardest subject ever :( :'(
-
Can someone help me for ques. 36 in OCT/NOV 1997?
can u send me the paper i dont have it or atlst write the comp que
Well i ll write the ques.
"Which structure is that of an alkane?
A.Ethanoic acid
B. Propanol
C. Ethyl Ethanoate
D. Pentane"
-
cn any1 plz attach chem ppr 1 oct08????????
-
Can someone help me for ques. 36 in OCT/NOV 1997?
can u send me the paper i dont have it or atlst write the comp que
Well i ll write the ques.
"Which structure is that of an alkane?
A.Ethanoic acid
B. Propanol
C. Ethyl Ethanoate
D. Pentane"
pentane
-
cn any1 plz attach chem ppr 1 oct08????????
download it frm freeexampapers.com
-
pentane
Ya well thats wat i thought too bt the mark scheme says its ethyl ethanoate :-\
so that means the mark scheme is wrong???
-
Can someone explain Nov 03 Q 16 aaanndd Jun 04 Q15? Thanks
-
pentane
Ya well thats wat i thought too bt the mark scheme says its ethyl ethanoate :-\
so that means the mark scheme is wrong???
lemme chk this out it cannot be ethl ethanoate wait a sec
-
Can someone help me for ques. 36 in OCT/NOV 1997?
An alkene is a hydrocarbon with a C=C double bond
B
-
pentane
Ya well thats wat i thought too bt the mark scheme says its ethyl ethanoate :-\
so that means the mark scheme is wrong???
lemme chk this out it cannot be ethl ethanoate wait a sec
it cannot be if consider it on the basis of a single bond den all of dem have single bonds even the basic formula of CnH2n+2 doesnt apply den how is it possible
-
Can someone explain Nov 03 Q 16 aaanndd Jun 04 Q15? Thanks
bond breaking endo n bond formin exo
thts y x n y bond break so weak as d reaction exo i hope u get it n as far d other q in y it has 2 be more as its excess so y inc. hm me 2 also dnt knw hw 2 explain tht bt i hope u gt d other 1
-
lemme chk this out it cannot be ethl ethanoate wait a sec
it cannot be if consider it on the basis of a single bond den all of dem have single bonds even the basic formula of CnH2n+2 doesnt apply den how is it possible
[/quote]
I have no idea.....
i think the mark scheme is wrong cos many times it happened to the other papers....
So the ans. should be pentane
-
Can someone explain Nov 03 Q 16 aaanndd Jun 04 Q15? Thanks
Nov 03 Q 16 decreases since hydrogen is lighter than oxygen and increases
Jun 04 Q15 C since weak bonds take little energy to break and strong bonds give out a lot of energy when they are made
-
Can someone explain Nov 03 Q 16 aaanndd Jun 04 Q15? Thanks
the second que goes like this
energy required to break the bonds - energy required to form bonds
so if the bonds are weaker less energy will be required to break dem n if the bonds formed r strong den more energy will be required to form dem n thus the answer u get will be neative indicating it is exo
-
lemme chk this out it cannot be ethl ethanoate wait a sec
it cannot be if consider it on the basis of a single bond den all of dem have single bonds even the basic formula of CnH2n+2 doesnt apply den how is it possible
I have no idea.....
i think the mark scheme is wrong cos many times it happened to the other papers....
So the ans. should be pentane
[/quote]
no dude how can the markin scheme be wrong can any one else answer this
-
cn any1 plz attach chem ppr 1 oct08????????
download it frm freeexampapers.com
That notorius website
-
ahm...does any1 knw wat difference it makes if the solution is concentrated or not during electrolysis??
-
It does
concentrated solution means higher current and faster reaction
-
lemme chk this out it cannot be ethl ethanoate wait a sec
it cannot be if consider it on the basis of a single bond den all of dem have single bonds even the basic formula of CnH2n+2 doesnt apply den how is it possible
I have no idea.....
i think the mark scheme is wrong cos many times it happened to the other papers....
So the ans. should be pentane
it has to be pentane...
it is soo surely an alkane
good luck for ur exam anyway//
no dude how can the markin scheme be wrong can any one else answer this
[/quote]
-
I have no idea.....
i think the mark scheme is wrong cos many times it happened to the other papers....
So the ans. should be pentane
no dude how can the markin scheme be wrong can any one else answer this
[/quote]
Well bt it cant b any other ans!!!!!!!
Cos it says "STRUCTURE OF ALKANE"
It cant b ethy ethanoate which is in the mark scheme!!!!
-
I have no idea.....
i think the mark scheme is wrong cos many times it happened to the other papers....
So the ans. should be pentane
no dude how can the markin scheme be wrong can any one else answer this
Well bt it cant b any other ans!!!!!!!
Cos it says "STRUCTURE OF ALKANE"
It cant b ethy ethanoate which is in the mark scheme!!!!
[/quote]
hmm i noe hey astar u r a tuto ryt can u solve this 4 us
-
Can someone help me for ques. 36 in OCT/NOV 1997?
can u send me the paper i dont have it or atlst write the comp que
Well i ll write the ques.
"Which structure is that of an alkane?
A.Ethanoic acid
B. Propanol
C. Ethyl Ethanoate
D. Pentane"
definitely pentane- the only hydrocarbon. Pentane is a hydrocarbon
-
Can someone help me for ques. 36 in OCT/NOV 1997?
can u send me the paper i dont have it or atlst write the comp que
Well i ll write the ques.
"Which structure is that of an alkane?
A.Ethanoic acid
B. Propanol
C. Ethyl Ethanoate
D. Pentane"
definitely pentane- the only hydrocarbon. Pantane is a hydrocarbon
ok i think all of us say its pentane so tht means the marking scheme is wrong
By the way Thanks all of u :)
-
It does
concentrated solution means higher current and faster reaction
yeh but does it affect results at the electrodes...i mean whther the metal or hydrogen is reduced?
-
Can someone help me for ques. 36 in OCT/NOV 1997?
can u send me the paper i dont have it or atlst write the comp que
Well i ll write the ques.
"Which structure is that of an alkane?
A.Ethanoic acid
B. Propanol
C. Ethyl Ethanoate
D. Pentane"
definitely pentane- the only hydrocarbon. Pentane is a hydrocarbon
Ok then thanks!!!
So the final and conformed ans. is "pentane"!!!
Thank u for the help from everyone :)
-
yes and if the ms says otherwise it is WRONG!
-
Can someone help me for ques. 36 in OCT/NOV 1997?
can u send me the paper i dont have it or atlst write the comp que
Well i ll write the ques.
"Which structure is that of an alkane?
A.Ethanoic acid
B. Propanol
C. Ethyl Ethanoate
D. Pentane"
definitely pentane- the only hydrocarbon. Pentane is a hydrocarbon
Ok then thanks!!!
So the final and conformed ans. is "pentane"!!!
ya
-
It's pentane ofcourse
-
how are you people studying for chemistry paper 1?
-
Solve as much past papers as you can and if you see you got some weak points in certain points go through your notes or textbook quickly
-
how are you people studying for chemistry paper 1?
Just practice doing past papers.... Dats all i do for every paper :D
-
ahm...can some1 kindly answer ma question on the previous page ???
-
ahm...can some1 kindly answer ma question on the previous page ???
more dilute means h+ will be discaharged n OH- but if the halides r present OH- will not discharge even in dilute actually the best thing u can do is jus go according to the series
-
please help me with this: M/J 2007, Q16
please explain why is the answer c ?(1 and 2 only)
???
-
Helpp with Q 1 Jun 05!
-
Ok I don't get Q2 as well, so unprepared :( I hate chhemmm
-
Q1)c
Q2)b
-
I just realized the paper I was looking at has a diff code thing its 9701 not 0620 :S
-
Ok I don't get Q2 as well, so unprepared :( I hate chhemmm
dude the first one is see which is a metal it is a solid in solids molecules are arranged in an orderly manner rememba sumthin
n the second one only rise in temp is wht we have to care abt so no clock ok
-
Haha anyway I answered you for 0620
-
Lol I have no idea why the school would put this in our past paper booklets! I was freaking out :p
-
i think u r dozzed off wid chem or u have not even touched the book uptill now
-
Lol I have no idea why the school would put this in our past paper booklets! I was freaking out :p
which great skool do u belong to
i think dey did this so tht u guyz freak out n study hard
-
Hahaha nice theory! lol
-
please someone answer my previous question and this one too: Q 24 M/J 2007 ???
for Q24, how do we know that chlorine would displace potassium from potassium bromide and iodine won't
Please help...
Thanks in advance
-
please someone answer my previous question and this one too: Q 24 M/J 2007 ???
for Q24, how do we know that chlorine would displace potassium from potassium bromide and iodine won't
Please help...
Thanks in advance
reactivity decreases down the group in grp7
a more reactive halogen displaces a less reactive one 4rm its compound
-
please someone answer my previous question and this one too: Q 24 M/J 2007 ???
for Q24, how do we know that chlorine would displace potassium from potassium bromide and iodine won't
Please help...
Thanks in advance
Chlorine is more reactive than bromine, so it will displace bromine from its compounds. Iodine is less reactive so won't displace bromine.
-
According to the halogens..
F
Cl
Br
I
At
So the KBr can react with Cl making a displacement rxn but the Kbr cant react with I because I is less reactive than Br..
So the answer is B
-
f is the most reactive halogen and so can displace all the others...as u go down reactivity decreases
F
Cl
Br
I
At
so Cl would be able to displace all the halogens which are below them but not above and so on!
-
thanks a lot everyone!
someone please try answering my previous question (M/J 2007, Q16-----the one about redox reaction) Why is the answer C?
-
thanks a lot everyone!
someone please try answering my previous question (M/J 2007, Q16-----the one about redox reaction) Why is the answer C?
since in equation 3 no reactants have lost or gained electrons, oxygen or hydrogen!
-
thanks a lot everyone!
someone please try answering my previous question (M/J 2007, Q16-----the one about redox reaction) Why is the answer C?
since in equation 3 no reactants have lost or gained electrons, oxygen or hydrogen!
Ya,but why is equation 1 and 2 REDOX?
1 and 2 are only oxidation, not reduction...
please help...
-
thanks a lot everyone!
someone please try answering my previous question (M/J 2007, Q16-----the one about redox reaction) Why is the answer C?
since in equation 3 no reactants have lost or gained electrons, oxygen or hydrogen!
Ya,but why is equation 1 and 2 REDOX?
1 and 2 are only oxidation, not reduction...
please help...
i dnt quite get it but i guess since 1 and 2 r reversible reactions they r oxidised in forward and reduced in backward rit? :-\
-
S has many oxidation states including -2,0,2,4,6...
in this particular reaction the oxidation state of S is "+2"
a decrease in oxidation state - reduction
an increase in oxidation state - oxidation
1.) S + O2 -> SO2
here at the left handside, as sulphur exists itself (not compound), the oxidation state is 0
at the right hand sidde it forms a compound and gains an oxidation state of +2 = this is oxidation
whereas O has an oxidation state of "0" in the left hand side and decreases to -4 in the right hand side
this is reduction
therefore its redox
-
thanks a lot everyone!
someone please try answering my previous question (M/J 2007, Q16-----the one about redox reaction) Why is the answer C?
since in equation 3 no reactants have lost or gained electrons, oxygen or hydrogen!
Ya,but why is equation 1 and 2 REDOX?
1 and 2 are only oxidation, not reduction...
please help...
it's a little difficult to explain
but i'll try...in the first one Sulphur gains oxygen atoms(oxidation) but oxygen gains electrons(reduction).
in the second one sulphur gains oxygen but oxygen gains electrons
whereas in third one although oxygen is gained, there is no transfer of electrons and hydrogen does not lose oxygen but combines with SO4
It's very difficult to explain.
* Oxygen's oxidation state reduces in the covalent bond it forms with sulphur
-
its not a que which can be explaind the best thing u can do is to go through ur notes n eat ur teachers head if u get her n u have time
-
S has many oxidation states including -2,0,2,4,6...
in this particular reaction the oxidation state of S is "+2"
a decrease in oxidation state - reduction
an increase in oxidation state - oxidation
1.) S + O2 -> SO2
here at the left handside, as sulphur exists itself (not compound), the oxidation state is 0
at the right hand sidde it forms a compound and gains an oxidation state of +2 = this is oxidation
whereas O has an oxidation state of "0" in the left hand side and decreases to -4 in the right hand side
this is reduction
therefore its redox
for the second equation
i can notice the decrease in oxidation state of oxygen
but not sulphur
the oxidation state of sulphur doesn't change
---
maybe this too is called a redox...
sry
but i think the first one's explanation is correct
-
bye ppl g2g bst of luck 4 2morrow
-
S has many oxidation states including -2,0,2,4,6...
in this particular reaction the oxidation state of S is "+2"
a decrease in oxidation state - reduction
an increase in oxidation state - oxidation
1.) S + O2 -> SO2
here at the left handside, as sulphur exists itself (not compound), the oxidation state is 0
at the right hand sidde it forms a compound and gains an oxidation state of +2 = this is oxidation
whereas O has an oxidation state of "0" in the left hand side and decreases to -4 in the right hand side
this is reduction
therefore its redox
for the second equation
i can notice the decrease in oxidation state of oxygen
but not sulphur
the oxidation state of sulphur doesn't change
---
maybe this too is called a redox...
sry
but i think the first one's explanation is correct
sulphur gains oxygen atoms..so that is oxidation whereas oxygen's oxidation state falls which is reduction
-
ohh..tks
but in the first one i explained pereviously
the sulphur gains oxygen atoms and its oxidation state also increases..
this proves that it is oxidation
but...in the second equation the sulphur's oxidation state doesn't change...
-
ohh..tks
but in the first one i explained pereviously
the sulphur gains oxygen atoms and its oxidation state also increases..
this proves that it is oxidation
but...in the second equation the sulphur's oxidation state doesn't change...
oxidation is also the gain of oxygen atoms, which sulphur has gained.
-
in question 38 june 08......
-
S has many oxidation states including -2,0,2,4,6...
in this particular reaction the oxidation state of S is "+2"
a decrease in oxidation state - reduction
an increase in oxidation state - oxidation
1.) S + O2 -> SO2
here at the left handside, as sulphur exists itself (not compound), the oxidation state is 0
at the right hand sidde it forms a compound and gains an oxidation state of +2 = this is oxidation
whereas O has an oxidation state of "0" in the left hand side and decreases to -4 in the right hand side
this is reduction
therefore its redox
Thanks a lot
+rep for you :D
-
in question 38 june 08......
it is petroleum
-
thanks a lot everyone!
someone please try answering my previous question (M/J 2007, Q16-----the one about redox reaction) Why is the answer C?
since in equation 3 no reactants have lost or gained electrons, oxygen or hydrogen!
Ya,but why is equation 1 and 2 REDOX?
1 and 2 are only oxidation, not reduction...
please help...
it's a little difficult to explain
but i'll try...in the first one Sulphur gains oxygen atoms(oxidation) but oxygen gains electrons(reduction).
in the second one sulphur gains oxygen but oxygen gains electrons
whereas in third one although oxygen is gained, there is no transfer of electrons and hydrogen does not lose oxygen but combines with SO4
It's very difficult to explain.
* Oxygen's oxidation state reduces in the covalent bond it forms with sulphur
Thanks a lot!!!
+rep for you :D
-
in question 38 june 08......
C (petroleum)
-
Can u please tell me whats the answer for May/June 2008 Question 19
Mark scheme says D.. i think its C
Cause 2KOH --> H20 thats ph going from 14 - 7 so decreases :s why is it d in the ms its wrong rite?
-
Can u please tell me whats the answer for May/June 2008 Question 19
Mark scheme says D.. i think its C
Cause 2KOH --> H20 thats ph going from 14 - 7 so decreases :s why is it d in the ms its wrong rite?
There is excess KOH
pH of water increases from 7 to 13/14
-
can u explain further ... and please are u 100%?
-
can u explain further ... and please are u 100%?
yes im 100% sure. See when the two react, KOH is in excess..it still remains in the solution after the reaction is over. The pH of the solution increases as the alkali is in excess. I've tried my best to explain it.
-
can u explain further ... and please are u 100%?
yes im 100% sure. See when the two react, KOH is in excess..it still remains in the solution after the reaction is over. The pH of the solution increases as the alkali is in excess. I've tried my best to explain it.
luk man der is no other possibility by which the pH can increase so its simple tht KOH is in excess
-
Could someone help me with question 20 in november 2008. I don't understand y ph should increase...
-
Could someone help me with question 20 in november 2008. I don't understand y ph should increase...
hcl is uesd up na so the pH will increase
-
Nope......pH will decrease (acidic) bec nitric acid forms!
-
right, but hcl is already present, isnt that acidic enough
-
The answer is B
-
look.....first.hcl is used up so pH increases then nitric acid forms so it decreases!!!
-
but in the end, shudnt the ph remain the same?
-
No the pH will decrease as they said..there;'s no option for the pH to be "the same"
-
lool no barium nitrate is in the test tube not HCl. You add HCl to it, its pH will decrease from i gess 7 around 2. And no ppt will be formed cuz the BaCl2 produced will dissolve .
-
Oh!!!!!! yes, ur rite... barium is in the test tube. Thank you soo much
-
Nope......pH will decrease (acidic) bec nitric acid forms!
YEAH...THAT ONLY I WAS THINKING..... :)
-
look.....first.hcl is used up so pH increases then nitric acid forms so it decreases!!!
noh dude. nitric acid WONT be formed at all !!
The equation goes like this:
BaNO3 + 2HCl --> BaCl2 + H2O + NO2
-
Oh!!!!!! yes, ur rite... barium is in the test tube. Thank you soo much
llol Thanks for the +rep . I'd been stuck on -5 for eternity :-[
-
Thanks 4 correcting! ;D
-
Thanks 4 correcting! ;D
ur welcome :)
-
will someone help me in quetion 4 ,15, and 37 in nov.08
-
can any 1 plz post chemistry past papers from 93 _ 95 and their mark scheme.
thanx in advance
-
4 _ A ,cuz X is ionic so is solube in water and is the filterate while Y is organic so solube in organic solvents and is in the filterate too
15 _ A , cuz when 5g of X REACT WID 1000 cm , 500cm only react while the excess 500 are used to warm the mixture so when 500cm of water only react wid 5g then then all the 500cm react and there is no excess to warm the mixture and raise the temperature so the the decrease will be double
37 _ C cuz an acid will react with the carbonate to give bubbles of CO2
hope this helps
good luck ;) ;)
-
OK June 2005.
Which reacts with cold water only when finely powdered?
A. Calcium
B. Copper
C. Sodium
D. Magnesium
I put Sodium because its higher in the reactivity series, but the ms said magnesium...
WHY?? help urgently..?
-
I think because Mg can be powdered ?
-
4 _ A ,cuz X is ionic so is solube in water and is the filterate while Y is organic so solube in organic solvents and is in the filterate too
15 _ A , cuz when 5g of X REACT WID 1000 cm , 500cm only react while the excess 500 are used to warm the mixture so when 500cm of water only react wid 5g then then all the 500cm react and there is no excess to warm the mixture and raise the temperature so the the decrease will be double
37 _ C cuz an acid will react with the carbonate to give bubbles of CO2
hope this helps
good luck ;) ;)
Thanks man
-
I think because Mg can be powdered ?
Cant sodium be powdered????
-
am not a man... am a girl ;) :D
-
It can be cut by a knife but still not sure
-
srry girl anyways thanks
-
will someone help me in quetion 4 ,15, and 37 in nov.08
Q4 [A] --> well, its kinda hard to explain buh the main reason is becuz X being an ionic salt will dissolve (though all of them wont without heat) but Y wont being organic (like petrol), so u filter it out in 1, and in 2 its the opposite cuz being organic Y HAS TO dissolve in ethanol.
Q15 ---> im not really sure miself, i chose B (its wrong; the rite answer is A) cuz the amount of reactant is decreasing, so they need less energy to form a product.
Q37 [C]--> thats one of the easiest really. Any Carbonate upon reacting with an acid will always produce CO2, so u get bubbles of gas.
-
4 the june 2005 ques they want the metal that cant react wid cold water except wen finely powdered
so calcium can react even if its not powdered
and sodium th same thing
copper cant react
Mg reacts with steam and reacts SLOWLY wid water so wen we powder it it will react readily
gd luck ;)
-
cjeck your email in 20 mins
-
the answer is d cause chlorine is produced at the anode ,,, and because it bleaches the indicator the colour becomes white near the anode.....
and at the cathode the alkali is formed which turns indicator blue....
hope i helped,,,,....
Hey but what alkali is formed at the cathode
shouldnt hydrogen be formed at the cathode??
hydrogen forms at cathod ..see all non matels except for hydrogen forms at anode and all metal icludin hydrogen forms a cathode! if it molten hydrogen is not at anode and in aq and in concetrated hydrogen is formed....
-
OK June 2005.
Which reacts with cold water only when finely powdered?
A. Calcium
B. Copper
C. Sodium
D. Magnesium
I put Sodium because its higher in the reactivity series, but the ms said magnesium...
WHY?? help urgently..?
Well. cuz Na is in the 1st group so it WILL react with cold water. Cu is very unreactive so obviously it wont. So u have Mg and Ca.
Ca like u said is more reactive, so it will react more readily while Mg will have to altered alittle to make it react.
-
OK June 2005.
Which reacts with cold water only when finely powdered?
A. Calcium
B. Copper
C. Sodium
D. Magnesium
I put Sodium because its higher in the reactivity series, but the ms said magnesium...
WHY?? help urgently..?
Well. cuz Na is in the 1st group so it WILL react with cold water. Cu is very unreactive so obviously it wont. So u have Mg and Ca.
Ca like u said is more reactive, so it will react more readily while Mg will have to altered alittle to make it react.
mg is lower down the reactivity series so its most reactive
-
No the highest at the rectivity series is the most reactive
-
No the highest at the rectivity series is the most reactive
yup sorry thts wat i meant
im just so stressed
thx for correcting
-
No its okay
-
um sweetsh.. do u EVER go offline
-
Yes..
Actually if you wonder I keep my PC open during the day and check the forum from time to time..Just to make sure everything is going on in the proper way
-
Isnt a redox reactions when the reaction has oxidation and reduction at the same time???
The how come S + 2O2--> SO4 is a redox reaction???
-
oh, ur the admin ;D heheh
-
Isnt a redox reactions when the reaction has oxidation and reduction at the same time???
The how come S + 2O2--> SO4 is a redox reaction???
It isnt... :P
-
Isnt a redox reactions when the reaction has oxidation and reduction at the same time???
The how come S + 2O2--> SO4 is a redox reaction???
well i finally understood it
u see the oxidation is easy to get since sulphur gains oxygen atom
now reduction: the oxidation is where the oxygen here becomes from an atom of no oxidation state to losing being of oxidation state of -2 in SO4, thus lose of oxidation state is reduction . that's it ;D!
-
Could anyone please explain why the answer to November 2008 qn 23 is A?
-
OK June 2005.
Which reacts with cold water only when finely powdered?
A. Calcium
B. Copper
C. Sodium
D. Magnesium
I put Sodium because its higher in the reactivity series, but the ms said magnesium...
WHY?? help urgently..?
well its in the chapter "PERIODIC TABLE"..where one of the things u gotta learn is that from group II elements magnesium and beryllium react only with steam...and with cold water if powdered, to produce their oxide and liberate hydrogen..while as u knw otha elements of group II react with cold water to form their hydroxide and liberate hydrogen gas
-
Nov 2008 questions 15,20,29
help!..
-
Could anyone please explain why the answer to November 2008 qn 23 is A?
magnesium chloride is ALREADY a salt..thus won't react with anything let it be an acid or not to form anotha salt...thus A where that option has a cross!
-
15)a
20)b
29)b
-
I thought about it..and thought so. But, I did a bit of research and found that it could react! That's just too confusing :(
-
Nov 2008 questions 15,20,29
help!..
15) C...if it absorbs 10 from 1000cm^3 then it would absorb twice as much of heat from 500cm^3 since volume is halved!
20)HCL + BaNO3-->HNO3+BACL ....therefore the acidic nitric acid decrease the pH and since barium reacts with chlorine,therfore no precipitate
29)metals donot have 6 in their outa shell and always form ionic compounds thus B
-
I can't get this, what's the difference between molten and aqueos?
-
aquous means dissolved in water or solution
molten means just melted, in pure liquid form
-
Nov 2008 questions 15,20,29
help!..
15) C...if it absorbs 10 from 1000cm^3 then it would absorb twice as much of heat from 500cm^3 since volume is halved!
20)HCL + BaNO3-->HNO3+BACL ....therefore the acidic nitric acid decrease the pH and since barium reacts with chlorine,therfore no precipitate
29)metals donot have 6 in their outa shell and always form ionic compounds thus B
for 15 the answer is A not C since the reaction is enothermic !
buh i still dont get it how will the solution absorb more heat if it has been halved ???. This is what i made out of it: since one of th rectants is being halved you wud need only half the energy .
-
Nov 2008 questions 15,20,29
help!..
15) C...if it absorbs 10 from 1000cm^3 then it would absorb twice as much of heat from 500cm^3 since volume is halved!
20)HCL + BaNO3-->HNO3+BACL ....therefore the acidic nitric acid decrease the pH and since barium reacts with chlorine,therfore no precipitate
29)metals donot have 6 in their outa shell and always form ionic compounds thus B
for 15 the answer is A not C since the reaction is enothermic !
buh i still dont get it how will the solution absorb more heat if it has been halved ???. This is what i made out of it: since one of th rectants is being halved you wud need only half the energy .
It is just like physics. It takes double the amount of heat energy to increase the temperature of 1000 cm3 of water by 1 degree celsius, than to increase the temperature of 500, by 1 degree. Thus, if there is half the volume of water, and the same amount of heat, the temperature change will be double. Take an example of sharing money (assume, it is heat) between 10 children (assume its 1000 cm3 of water). If we half the number of children to 5 (volume decreased to 500), the amount of money each will get, will double (temperature increases). :)
-
wow i-insane....im soooo impressed...ur soooo smart.....n rely gud n effective eg.....
all da best 4 tom....Take care n cya :)
-
cud any1 plz xplain why is the answer for Q13 un nov. 2008 is B and not D?
-
Quote from: GodOfWar on Today at 08:51:01 PM
Quote from: sweetest angel on Today at 08:30:54 PM
Quote from: cockyxrocker on Today at 08:19:18 PM
Nov 2008 questions 15,20,29
help!..
15) C...if it absorbs 10 from 1000cm^3 then it would absorb twice as much of heat from 500cm^3 since volume is halved!
20)HCL + BaNO3-->HNO3+BACL ....therefore the acidic nitric acid decrease the pH and since barium reacts with chlorine,therfore no precipitate
29)metals donot have 6 in their outa shell and always form ionic compounds thus B
for 15 the answer is A not C since the reaction is enothermic !
buh i still dont get it how will the solution absorb more heat if it has been halved . This is what i made out of it: since one of th rectants is being halved you wud need only half the energy .
It is just like physics. It takes double the amount of heat energy to increase the temperature of 1000 cm3 of water by 1 degree celsius, than to increase the temperature of 500, by 1 degree. Thus, if there is half the volume of water, and the same amount of heat, the temperature change will be double. Take an example of sharing money (assume, it is heat) between 10 children (assume its 1000 cm3 of water). If we half the number of children to 5 (volume decreased to 500), the amount of money each will get, will double (temperature increases).
thanks a lot! that really helped!
-
hello? cud any1 answer my q please?
one more =)q 36..why is it A? same year-->2008..thanx
-
may june ryt?
well cos all da oders do produce carbon dioxide lol
plus da option for A is HCL + C
ders no oxygen involved so how wud it give co2
-
ya 4 q13....itz lead cuz it says low in da reactivity series.....so lead is lower den sodium...n it has 2 b molten cuz if in solution....hydrogen ll b liberated instead of da metal itself.....wich wnt mach wid da ques
so itz B.....hope u understud.....Take care n all da best
-
thank you both =) but shafiq, i meant nov not may/june... thanx anyway=)
appreciated:)
-
oh lol its cos chlorination and filtration is for less polluted water not for water polluted wid fertilizers
i think lol
its definately not chlorination as chlorination is only used to kill bacteria
bt im not sure why filtration cant b used 0_0
-
hmmm..that exactly wat i was wandering about....hmmm...it's okay thanx anyway:)
sry but i have got one more question:P..wat is meant by the "oxidation state"?
-
gah i forgot lots of what i studied for paper 3...
tried my best to recover :P but ehhh i dont care anymore .. last exam.. dont care if i mess up :D :P
-
dont think that way - its 30% weightage dude!!
-
which salts are soluble in acids and which salts react with acids? ???
-
can anyone pls help me?
-
can anyone pls help me?
I don't think you need to know the solubility of salts in acids and which salts react with acids....
Im not sure...
-
Do hydrocarbons and polymers occur naturally? i saw this Q in one of the past papers...
plzz helpp
-
Do hydrocarbons and polymers occur naturally? i saw this Q in one of the past papers...
plzz helpp
im guessing hydrocarbons do
but polymers
well actually some occur natural so yes
-
Well their originality is from Dead animals and plants ?
Can anyone help me with Question 29 Paper 1 June 2004
how do we know the volume of Oxygen !
-
Well their originality is from Dead animals and plants ?
Can anyone help me with Question 29 Paper 1 June 2004
how do we know the volume of Oxygen !
the volume of oxygen is 30cm3
but the air i have no idea
i think its bcuz thts the maximum mark on the gas syringe
-
oh Thanks man
O.k one more and thats it lol
emm how about the same paper ( June 2004 ) paper 1 Question 19 ?
Why is the answer ammonia ?
-
Well their originality is from Dead animals and plants ?
Can anyone help me with Question 29 Paper 1 June 2004
how do we know the volume of Oxygen !
the volume of oxygen is 30cm3
but the air i have no idea
i think its bcuz thts the maximum mark on the gas syringe
its because oxygen is 21% of air,
so....just work out of the options available which would give the correct answer....
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REP + Thanks Bani
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oh Thanks man
O.k one more and thats it lol
emm how about the same paper ( June 2004 ) paper 1 Question 19 ?
Why is the answer ammonia ?
bcuz al does not disslove in excess and zinc does so u can distinguish between them
for sodium hydroxide
both dissolve in excess so u cant tell the difference
gettit/?
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Ohhhhh yeah yeah thats the thing about the cations ans anions sheet that we had to learn
Thanks man appreciated
REP+ for u :D
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hey sorry a few questions as well
In Nov 2000 Question 23
Why is it B ?
And June 2003 Question 16
No idea why its C
But is it because Copper II when in solution is blue ?
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hey sorry a few questions as well
In Nov 2000 Question 23
Why is it B ?
And June 2003 Question 16
No idea why its C
But is it because Copper II when in solution is blue ?
what has colour to do with it?
i really dont know why they use co2 instead of co sorry
i dont have nov 2000 dunno the question sorry bout tht too
thx amy + rep 2 u 2 ;D
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Nov 2000
B because in a displacement reaction, a more reactive element displaces the less reactive one, therefore, CHLORINE is more reactive than BROMINE, and displaces it, hence BR2 is formed, which turns the solution brown!
Read up displacement reactions in ''The Periodic Table''
and for m/j 03
it is white to blue because it is 'hydrated'. it i s a copper sulphate salt, reversible reaction, when u add water it goes from white to blue. when u heat it, water is taken away, so blue to white!
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sorry amy i had the wrong paper
yes it is at first hydrated(with water) then dehydrates
notice they r asking about the products not reactants
white toblue cuz when heated it turns white
then if u add water it turns blue
heat energy is taken out bcuz when u turn hydrated copper 2 sulphate its exothermic
but when opposite its endo
@angelll, u r right too
i just wnted to explain the energy part as well
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wat is an oxidation state??? i hhave no ide, i never paid attention in class when da teacher was teaching us ><, is it da same as valency??
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wat is an oxidation state??? i hhave no ide, i never paid attention in class when da teacher was teaching us ><, is it da same as valency??
you can say tht yes
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thanks guys I owe u
REP+ for angell
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thnnxx =D
and guys this question made no sense to me at all
ryt 2004 nov
question 11
11. A substance X is heated in an evaporating basin until there is no further change.
mass of basin and contents
before heating 25.52 g
after heating 26.63 g
What could X be?
A copper
B copper(II) carbonate
C copper(II) oxide
D hydrated copper(II) sulphate
da answer is a bt i hav no idea why
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thnnxx =D
and guys this question made no sense to me at all
ryt 2004 nov
question 11
11. A substance X is heated in an evaporating basin until there is no further change.
mass of basin and contents
before heating 25.52 g
after heating 26.63 g
What could X be?
A copper
B copper(II) carbonate
C copper(II) oxide
D hydrated copper(II) sulphate
da answer is a bt i hav no idea why
luk, u heat the copper and forms copper 2 oxide
which is a black powder
so mass increases
it cant be the others cuz they all give out either a gas or water or somat
gettit?
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yea :D
Thanks
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can u explain further ... and please are u 100%?
yes im 100% sure. See when the two react, KOH is in excess..it still remains in the solution after the reaction is over. The pH of the solution increases as the alkali is in excess. I've tried my best to explain it.
luk man der is no other possibility by which the pH can increase so its simple tht KOH is in excess
oo thanks i get it now :)
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any gave the paper?
how was it?
easy or hard?
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i did it
it was so easy
only 2-4 questions were tricky
and the rest of the exam was easy
good luck for all
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easy paper....and yeah only a couple of questions were tricky....dont freak out and just calm down...ok...good luck
and i am done with papers...(momentarily cuz i am giving more in november).....YAYY!!!!!!!!!!!!
;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D
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it wwasss soooo easyyy xDDD
i was only confused about da last question
as memory serves da answer shudve been naphta bt der was no choice ><
but i put paraffin =D
wich i think is ryt
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naphta is actually used for a feedstock por plastics i think. so it was parafin, also named kerosene
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no the last answer is A :P :P
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what was the last question??
and anyway for the question on aircraft fuel its definately paraffin theres a exact same
past question
like this and then i had looked at my text and it said that parrafin=kerosine
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they even gav da clue...that its used in aircraft........
so its paraffin/kerosine
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i found the paper very tricky i donno why but it was not gud 4 me
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i found the paper very tricky i donno why but it was not gud 4 me
u mean chemistry!!!!
well....maybe cuz few questions wr tricky!!
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accordin' to me..they kept the best for the last ;D
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yes..very true! but liked the exam though!! just struggled in 2 question but other than that it was gd for me!!