IGCSE/GCSE/O & A Level/IB/University Student Forum
Qualification => Subject Doubts => IGCSE/ GCSE => Sciences => Topic started by: ~HyDrOgEn~ on May 29, 2010, 03:53:10 pm
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Any Doubts so i can help! :D
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Any Doubts so i can help! :D
got any note? TOTAL REVISION NOTES.
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what is condesation polymerization
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what is condesation polymerization
Polymerization in which there is loss of water
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can u show me with 1 example
i willl br=e very thankfull to u
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let's consider formation of a dipeptide
monomer is amino acid
check the attachment.
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REVISION NOTES!
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???
????
?????
????
???
??
?
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ugh chemistry ... NVM
[/shadow]
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lol...yup I'll get you notes....but tell me topics you have difficulty with
Why do people hate chemistry? ::)
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lol...yup I'll get you notes....but tell me topics you have difficulty with
Why do people hate chemistry? ::)
I have always wondered, why ?
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I have always wondered, why ?
Its cuz people dont want to learn a science where u have to byheart and mug something...
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Its cuz people dont want to learn a science where u have to byheart and mug something...
loool. Chemistry is mugging up??!!! :@ :S
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loool. Chemistry is mugging up??!!! :@ :S
No man, ill tell u about chem...
its like no other subject... its Either u GET it or u DONT.
If ur made to understandu will or else u wont, no matter how much help u take..
and then the interest starts to lack. behind... thts the problem
The most interesting in the 3 sciences is PHYSICS, then maybe BIO ( even though i don take it) and CHEM LAST LAST.....
Physics is GENERAL SENSE applied.
=]
@ hydrogen , i was wondering if u have TOTAL REVISION NOTES on all topics. Its okay if u dont :D
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Its cuz people dont want to learn a science where u have to byheart and mug something...
My friend. Business subjects are where you memorise stuff.
With science you have to have a strong foundation, then you can answer any question.
Weak concept = fail = science-hater
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My friend. Business subjects are where you memorise stuff.
With science you have to have a strong foundation, then you can answer any question.
Weak concept = fail = science-hater
Not necessariy.
Science needs conceptual understanding. But a weak concept can even gain good marks these days.
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But a weak concept can even gain good marks these days.
Not with the CIE.
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can anyone draw the protein structure ((what do th R in the structure stand for ??))
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Here is the structure with the CONH or amide linkage.
You dont need to know whats in the box so just leave it empty.
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ummmmmmmmmmmm
yh bout the notes
i dont get the forward reactoin and bakward thingy
+ im lost in stociometry
every ppr i do i get a darn B
glad if u cud help
thx
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Post some sample questions....
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ummmmmmmmmm
kk
heres one
oct/nov 2005
http://freeexampapers.com/FreeExamPapers.com_.php?__lo=SUdDU0UvQ2hlbWlzdHJ5L0NJRS8yMDA1IE5vdi8wNjIwX3cwNV9xcF8zLnBkZg==
question 3
question 6
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please specify what you don't understand :P
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y dont u guys jus gimme sum notes on those because
i actually have 2 do pprs fast
not 2 be rude or nythin....
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notes are on here...browse the reference material
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notes are on here...browse the reference material
ummmm
nuthin on stochiometry an that forward an bakward reactions....
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check the attachment. Stoichio. read only uptil page 3. beyond that is AS stuff...which you don't need now.
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thx
nyway
whos this nithdreamer chap???
nice notes over there as well
but still no equilibrium...
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whos this nithdreamer chap???
Does that matter?
but still no equilibrium...
http://www.docbrown.info/page04/4_74revNH3.htm
go through
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Does that matter?
wow! touchy :o
nah
jus complimentin
send him my regards if u no him :P
hehehehe
thx fr the links
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wow! touchy :o
nah
jus complimentin
send him my regards if u no him :P
hehehehe
thx fr the links
Indeed she would be. Do you have an issue with that ?
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do i?
u tell
because i dont c y u ppl seem 2 be jumpy
@nid: sry if hurt or nythin didnt realiz if i did
@ari bben canaan: wats up with u dude?????
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do i?
u tell
because i dont c y u ppl seem 2 be jumpy
@nid: sry if hurt or nythin didnt realiz if i did
@ari bben canaan: wats up with u dude?????
For once would you consider writing in full sentences using the whole word. Because what you have written is plain gibberish to me.
Seriously.
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For once would you consider writing in full sentences using the whole word. Because what you have written is plain gibberish to me.
Seriously.
hhehehe
yh i no
i have a nack of doin that
oops did it again
SORRY!!!
hehehehe
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nyway another doubt
may/june 2009
question 5b
how the heck do u find that out???
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nyway another doubt
may/june 2009
question 5b
how the heck do u find that out???
Please post the question here.
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Please post the question here.
http://freeexampapers.com/FreeExamPapers.com_.php?__lo=SUdDU0UvQ2hlbWlzdHJ5L0NJRS8yMDA5IEp1bi8wNjIwX3MwOV9xcF8zLnBkZg==
there u go
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For once would you consider writing in full sentences using the whole word. Because what you have written is plain gibberish to me.
Seriously.
If thats Gibberish to u , then i wonder wat english is to u ... Muahah ! =D
@ Furqan - Do post some notes to me cuz these guys dont seem to understand... -.-
guys i asked if u cud POST SOME PROPER NOTES ! that would be, attach the dam files and say " here you go"... Instead of uploading sh*t, and going like just go till page 3 or something !.
Walao mehhh!
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shazil u moron
hehehhehe
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No man, ill tell u about chem...
its like no other subject... its Either u GET it or u DONT.
If ur made to understandu will or else u wont, no matter how much help u take..
and then the interest starts to lack. behind... thts the problem
The most interesting in the 3 sciences is PHYSICS, then maybe BIO ( even though i don take it) and CHEM LAST LAST.....
Physics is GENERAL SENSE applied.
=]
@ hydrogen , i was wondering if u have TOTAL REVISION NOTES on all topics. Its okay if u dont :D
Sorry man i dont have Revision notes , but if you have any questions, then don,t hesitate, iam here , :D
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the guys banned
heheheh
idiot really
i warned him
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sumthin bout showin attitude 2 a mod
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haha u guys crack me up!! :D ;D
anyways i just wanted to ask for good website for chem please :-[
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http://thenightdreamer.files.wordpress.com/2009/11/igcse-chemistry1.pdf
there u go
no biggie 2 me
heheheh
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Not necessariy.
Science needs conceptual understanding. But a weak concept can even gain good marks these days.
yes understanding will gain marks for any student as long as they understand it well!
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Alright, I've got a Chemistry doubt here:
Explain why the formula for the compound formed when Sodium and Chlorine react is NaCl and not NaCl2
Note: this is not in the past papers, it's from my chemistry textbook.
Thanks in advance :)
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Because Na is a group one metal. When it ionizes, it loses one outer electron to become stable, thus forming Na+ .
In addition, when chlorine gains an electron to become stable, it gains one electron (from Na atom), forming Cl- .
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because na has valency of +1
so it can only give 1 electron
and cl has valency of -1 so it can only accept an electron
+1+(-1)=0
so...
NaCl
hope u undertand
cheers mate!!!
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Alright, I've got a Chemistry doubt here:
Explain why the formula for the compound formed when Sodium and Chlorine react is NaCl and not NaCl2
Note: this is not in the past papers, it's from my chemistry textbook.
Thanks in advance :)
Na has a valency of +1 and Cl of -1
Na loses 1 atom nd Cl accepts 1.
so it NaCl
Mg loses 2 Cl accepts 1
MgCl2
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Na has a valency of +1 and Cl of -1
Na loses 1 atom nd Cl accepts 1.
so it NaCl
Mg loses 2 Cl accepts 1
MgCl2
LOLS! I think you mean electron rather than atom! :P
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Thanks Guys...I understand the concept, but I didn't know how to put it in words, thanks so much :)
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LOLS! I think you mean electron rather than atom! :P
yeah i meant electrons of atoms.
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could soeone please explain to me the forward and backward reactions and the equilibrium thingy... i dont get them...
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could soeone please explain to me the forward and backward reactions and the equilibrium thingy... i dont get them...
N2+3H2=2NH3
when the reaction frm lft to ryt is equal i mean that N and H react at the same rate as NH3 decomposes then it is in quilibrium.
no net change.
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N2+3H2=2NH3
when the reaction frm lft to ryt is equal i mean that N and H react at the same rate as NH3 decomposes then it is in quilibrium.
no net change.
The rate of reaction to be exact. An increase in pressure, decrease in temperature will favour the forward reaction (yield of ammonia) in the haber process.
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could soeone please explain to me the forward and backward reactions and the equilibrium thingy... i dont get them...
Is this what you wanted? Please see attached.
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The rate of reaction to be exact. An increase in pressure, decrease in temperature will favour the forward reaction (yield of ammonia) in the haber process.
habers process is done for commercial output of ammonia and there also comes a time for equilibruim in this reaction but the values r to get d highest yield of ammonia possible for commercial output.
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question 1
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question 1
its because organic compounds are not soluble in water and are in ethanol, ethanol is an organic solvent
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Okay, I have a question.
May/June 2004, Paper 3, Question 4, (b)(ii)
Why the difference between the height of the precipitate between Iron (II) and Iron (III) salts?
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Questions! :D
i) how do you draw the structure of the polymer formed from but-2-ene?
ii) How do you deduce the formula of the alkene which has a relative molecular mass of 168?
is it something to do with the empirical formula of... idk CnH2n hence 3n = 168 ... blahblah
lol help please! THANKS.
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Okay, I have a question.
May/June 2004, Paper 3, Question 4, (b)(ii)
Why the difference between the height of the precipitate between Iron (II) and Iron (III) salts?
OK, We know from the graph that 12cm3 of aqueous sodium hydroxide was needed to react with 4cm3 of aqueous iron(III) chloride. Because they were all at 1.0 mol/dm3, we therefore realise that 1 mole of aqueous iron (III) chloride reacted with 3 moles of aqueous sodium hydroxide. Therefore, the formula for the precipitate is Fe(OH)3.
For iron (II) chloride, we know the formula of the precipitate to be Fe(OH)2, and so for the same volume of aqueous iron (II) chloride - 4cm3, we know 8cm3 of sodium hydroxide was required. Therefore, you would need to draw the maximum height of the precipitate when volume has reached 8cm3.
Hope this has helped! ;D
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i) how do you draw the structure of the polymer formed from but-2-ene?
Here we go!
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Here we go!
THANKS :D
ii) How do you deduce the formula of the alkene which has a relative molecular mass of 168?
is it something to do with the empirical formula of... idk CnH2n hence 3n = 168 ... blahblah
lol help please! THANKS.
:D
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ii) How do you deduce the formula of the alkene which has a relative molecular mass of 168?
is it something to do with the empirical formula of... idk CnH2n hence 3n = 168 ... blahblah
lol help please! THANKS.
We know C has Ar of 12 and H is 1. So by using CnH2n:
12n + 2n = 168
So n = 12
So C12H24
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We know C has Ar of 12 and H is 1. So by using CnH2n:
12n + 2n = 168
So n = 12
So C12H24
THANKS ;D
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HI i have a pro
M/J 2002
q5 whole ms isnt there.....
can somebody pls tell me thx a lot...........
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Frnds sorry but one more q
4 c i
can somebody explain me how did one get that ans..................
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HI i have a pro
M/J 2002
q5 whole ms isnt there.....
can somebody pls tell me thx a lot...........
Gosh, how many times do I have to say this. Only joking, it's not you're fault for not knowing! :D
Here are the answers, not mark scheme but they are perfectly acceptable.
the a) part?
Liquids take the shape of the container, they maintain their volume. The intermolecular forces in liquids are significant and therefore, they do not expand to occupy all the space available (as gases do). A given mass of liquid has a fixed volume. also molecules in liquid have less k.e as compared to that of gases.Particles in gases have very weak intermolecular forces and high kinetic energy, hence the particles move independent of each other and occupy the space available to them.
b)i) rate= time and volume. In other words, its the volume produced and the time taken.
ii) CO2 due to lower molecular mass. or less density
The equation you need to use is:
Volume of gas (in dm3)
Moles of gas = --------------------------
24
Note to convert cm3 to dm3, divide quantity by 1000 (e.g. 20cm3/1000=0.02dm3)
This is the proper theory and equation behind my calculations below.
Here are the answers for 5) c) as requested:
i) Moles of C4H6: 0.02/24=0.000833
From equation, we know 2 moles of C4H6 reacts with 11 moles of O2
Therefore, moles of O2: 0.000833*5.5=0.00458
Therefore, volume of O2: 4.58*24*1000=110cm3
ii) From equation, we know 2 moles of C4H6 produces 8 moles of CO2
Therefore, moles of CO2: 0.000833*4=0.00333
Therefore, volume of CO2: 0.00333*24*1000=80cm3
iii) From equation, we know 2 moles of C4H6 produces 6 moles of H2O
Therefore, moles of H2O: 0.000833*3=0.0025
Therefore, volume of H2O: 0.0025*24*1000=60
Therefore, total volume of gases is simply volume of CO2 + volume of H2O:
80+60=140cm3
Alternatively, 8+6=14, so 2 moles of C4H6 produces 14 moles of products
Therefore, moles of products: 0.000833*7=0.00583
Therefore, volume of products: 0.00583*24*1000=140cm3
For part d), you use this formula:
Mass
Moles = ------
Mr
d) From the above equation, 1 mole of butyne forms 3 moles of water
Number of moles of butyne reacted: 9/54=0.167
Number of moles of water formed: 0.167*3=0.5
Mass of water formed: 0.5*(2+16)=9g
I hope this has helped. :D
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Frnds sorry but one more q
4 c i
can somebody explain me how did one get that ans..................
Right, the molecular formula is simply the formula showing the type and number of each element present in a molecule. So very simple, just count the number of carbon, oxygen and atoms. The answer is C6H8O6.
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Right, the molecular formula is simply the formula showing the type and number of each element present in a molecule. So very simple, just count the number of carbon, oxygen and atoms. The answer is C6H8O6.
but there are OH groups also so i thought that it could be alcohol but its not like that right ???????????????
and also same q paper q 7 biii.......................pls
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One more q
do we have cyclic hydrocarbons i guess one q had come abt properties
can somebody give info abt topics related to this..........
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OK, We know from the graph that 12cm3 of aqueous sodium hydroxide was needed to react with 4cm3 of aqueous iron(III) chloride. Because they were all at 1.0 mol/dm3, we therefore realise that 1 mole of aqueous iron (III) chloride reacted with 3 moles of aqueous sodium hydroxide. Therefore, the formula for the precipitate is Fe(OH)3.
For iron (II) chloride, we know the formula of the precipitate to be Fe(OH)2, and so for the same volume of aqueous iron (II) chloride - 4cm3, we know 8cm3 of sodium hydroxide was required. Therefore, you would need to draw the maximum height of the precipitate when volume has reached 8cm3.
Hope this has helped! ;D
Ohmigod. I actually feel stupid now. Hahah. Thanks. That really did it. ^.^
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HEy guys ,i'm really in trouble, the problem is that my chemistry guide(bob berry) is missing an important page(Pg 33 to 34) ,about excess reagents and coincidentally ,i always mess up that question and lose marks,so could someone scan the page off the guide and post it,or even a picture would do, i'm sure you''ll wil understand ,thanks! :D ;) :) :)
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but there are OH groups also so i thought that it could be alcohol but its not like that right ???????????????
and also same q paper q 7 biii.......................pls
You would not need to incorporate and OH groups, because they only ask for molecular formula. If they ask for the structual formula, then yes, but that would be complicated.
I'll give you an example:
Butane: Molecular formula - C4H10; Structual formula - CH3CH2CH2CH3.
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but there are OH groups also so i thought that it could be alcohol but its not like that right ???????????????
and also same q paper q 7 biii.......................pls
Depends on the q, here its vitamin C. Usually all vitamins contain -OH groups. Only for the structural formula you need to specify -OH and not the molecular formula. ;)
For Q.7 b)iii) There are 'n' number of types of chlorination. This depends on how much chlorine you use and which hydrocarbon you use.
When chlorination occurs it replaces one hydrogen atom from the hydrocarbon and forms HCl
E.g. Chlorination of methane::
H H
| |
H- C - H + Cl2 ------> H- C - Cl + HCl
| |
H H
CH4 + Cl2 ----> CH3Cl + HCl
Product:: Chloromethane (methyl chloride)
Similarly,
CH3Cl + Cl2 ----> CH2Cl2 + HCl
Product:: Dichloro methane (methylene chloride)
CH2Cl2 + Cl2 ----> CHCl3 + HCl
Product:: Trichloro methane (Chloroform)
CH3Cl3 + Cl2 ----> CCl4 + HCl
Product:: Tetrachloro methane (Carbon tetrachloride/Pylene)
I think you only need to know the names in bold. For your question, choose any of the following reaction BUT using butane and chlorine
Eg. C4H11Cl + Cl2 ----> C4H10Cl + HCl
OR to be safe give acc. to the ques
CH3-CH2-CH2-CH2-Cl + Cl2 ----> CH3-CH2-CH2-CHCL2 + HCl
H H H H H H H Cl
| | | | | | | |
H-C-C-C-C-Cl + Cl-Cl----> H-C- C-C-C-Cl + H-Cl
| | | | | | | |
H H H H H H H H
Don't understand anything.. pls. ask.. Just under the concept of chlorination ;) they may ask any other alkane next time
Draw the structures yourself you'll understand better
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One more q
do we have cyclic hydrocarbons i guess one q had come abt properties
can somebody give info abt topics related to this..........
They are not in our syllabus, from what I know they are just another method of representing hydrocarbons in a circular way < I am NOT sure!
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~VIN1094~, for w08, Q7) b) iii), I do not get it at all. The mark scheme says either 1 or 2-chloropropane is the product of the reaction, and that HCl is not a product.
Please explain, many thanks in advance.
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Depends on the q, here its vitamin C. Usually all vitamins contain -OH groups. Only for the structural formula you need to specify -OH and not the molecular formula. ;)
For Q.7 b)iii) There are 'n' number of types of chlorination. This depends on how much chlorine you use and which hydrocarbon you use.
When chlorination occurs it replaces one hydrogen atom from the hydrocarbon and forms HCl
E.g. Chlorination of methane::
H H
| |
H- C - H + Cl2 ------> H- C - Cl + HCl
| |
H H
CH4 + Cl2 ----> CH3Cl + HCl
Product:: Chloromethane (methyl chloride)
Similarly,
CH3Cl + Cl2 ----> CH2Cl2 + HCl
Product:: Dichloro methane (methylene chloride)
CH2Cl2 + Cl2 ----> CHCl3 + HCl
Product:: Trichloro methane (Chloroform)
CH3Cl3 + Cl2 ----> CCl4 + HCl
Product:: Tetrachloro methane (Carbon tetrachloride/Pylene)
I think you only need to know the names in bold. For your question, choose any of the following reaction BUT using butane and chlorine
Eg. C4H11Cl + Cl2 ----> C4H10Cl + HCl
OR to be safe give acc. to the ques
CH3-CH2-CH2-CH2-Cl + Cl2 ----> CH3-CH2-CH2-CHCL2 + HCl
H H H H H H H Cl
| | | | | | | |
H-C-C-C-C-Cl + Cl-Cl----> H-C- C-C-C-Cl + H-Cl
| | | | | | | |
H H H H H H H H
Don't understand anything.. pls. ask.. Just under the concept of chlorination ;) they may ask any other alkane next time
Draw the structures yourself you'll understand better
I am sorry VIn
but the q says that
Write a diff eqn for a substitutuin reaction between butane and chlorine
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~VIN1094~, for w08, Q7) b) iii), I do not get it at all. The mark scheme says either 1 or 2-chloropropane is the product of the reaction, and that HCl is not a product.
Please explain, many thanks in advance.
that is for c) iii) not b) iii) ;)
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I am soryy VIn
but the q says that
Write a diff eqn for a substitutuin reaction between butane and chlorine
I just gave you an example of methane... and how to name ...
I think you only need to know the names in bold. For your question, choose any of the following reaction BUT using butane and chlorine
Eg. C4H11Cl + Cl2 ----> C4H10Cl + HCl
OR to be safe give acc. to the ques
CH3-CH2-CH2-CH2-Cl + Cl2 ----> CH3-CH2-CH2-CHCL2 + HCl
H H H H H H H Cl
| | | | | | | |
H-C-C-C-C-Cl + Cl-Cl----> H-C- C-C-C-Cl + H-Cl
| | | | | | | |
H H H H H H H H
Don't understand anything.. pls. ask.. Just under the concept of chlorination ;) they may ask any other alkane next time
Draw the structures yourself you'll understand better
Got it?
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I just gave you an example of methane... and how to name ...
Got it?
i m again sry but where is butane in these reactions i can see is butyl chloride or whatever
sry for irritating but i m not getting the concept.............sry
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I am sorry VIn
but the q says that
Write a diff eqn for a substitutuin reaction between butane and chlorine
I was looking at the wrong part of the question, oops!
Anyway here is the answer to your question:
CH3-CH2-CH2-CH3 + Cl2 -> CH3–CH2–CH(Cl)–CH3 + HCl
That's right, isn't it?
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I was looking at the wrong part of the question, oops!
Anyway here is the answer to your question:
CH3-CH2-CH2-CH3 + Cl2 -> CH3–CH2–CH(Cl)–CH3 + HCl.
That's right, isn't it?
Yes it is, but this reaction is given in the question itself! They are asking for different reaction...
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Yes it is, but this reaction is given in the question itself! They are asking for different reaction...
~VIN1094~, apparantly that's the trap CIE wanted people to make. In the question, it does say a different equation for a substitution reaction between butane and chlorine, and not an additional chlorination of 1-chlorobutane.
So the product formed in my example is 2-chlorobutane as supposed to the 1-chlorobutane in the example.
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~VIN1094~, apparantly that's the trap CIE wanted people to make. In the question, it does say a different equation for a substitution reaction between butane and chlorine, and not an additional chlorination of 1-chlorobutane.
So the product formed in my example is 2-chlorobutane as supposed to the 1-chlorobutane in the example.
YES! You are right, I am a fool. Thanks :)
now i get it ;)
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YES! You are right, I am a fool. Thanks :)
now i get it ;)
ur not a fool , u've been helpin everyone in physics and math ...etc
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YES! You are right, I am a fool. Thanks :)
now i get it ;)
Hey, don't be so harsh on yourself! The notes you did on substitution reactions were really good anyway, so it wasn't all a waste!!!
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I was looking at the wrong part of the question, oops!
Anyway here is the answer to your question:
CH3-CH2-CH2-CH3 + Cl2 -> CH3–CH2–CH(Cl)–CH3 + HCl
That's right, isn't it?
r u sure?????????/
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r u sure?????????/
Tell me why it's not then :P It's been 'approved' by ~VIN1094~, so I don't see why it's wrong.
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some more doubts coming up...............
q4aii),iii)thensame q bii
q6bi its saying ammoniuum ion and ms is giving test abt nitrate ion............
q7b whole
thx in advance........
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4 a ii) Lead chloride and sodium nitrate
iii) Silver nitrate and potassium chloride
6 b i) Add sodium hydroxide, ammonia gas given off on warming, turns damp red litmus paper blue.
7 b) Mg + 2CH3COOH ? (CH3COO)2Mg + H2
Mg - 3/24 = 1/8
CH3COOH - 12/60 = 1/5
1 : 2 mole ratio
Mg is in excess as 1/8 * 2 = 1/4, which is greater than 1/5.
Compare the mole ratio of CH3COOH to hydrogen, 2:1.
1/10 * 24 = 2.4
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some more doubts coming up...............
q4aii),iii)thensame q bii
q6bi its saying ammoniuum ion and ms is giving test abt nitrate ion............
q7b whole
thx in advance........
4) a) ii) Pb(NO3)2 + 2NaCl -> PbCl2 + 2NaNO3
iii) Ag+ + Cl- -> AgCl
b) ii) Please click here (https://studentforums.biz/index.php/topic,8469.msg250425.html#msg250425).
6) b) i) Test: Add aqueous sodium hydroxide. Result: turns damp red litmus paper blue.
7) b) i) Moles of Mg = 3/24 = 0.125
Moles of CH3COOH = 12/60 = 0.200
Using ratios given in the equation, to compare, divide 0.2/2 = 0.100 moles of CH3COOH.
Therefore, magnesium is in excess.
ii) The one not in excess: ie. 0.1
iii) 0.1*24 =2.4dm3
Got it?
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May june 04 q 4 b 2 why until 8 mm it .. isnt there a range ?
Plus b 3 I have no idea what is going on i need help .. could any1 help?
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May june 04 q 4 b 2 why until 8 mm it .. isnt there a range ?
Plus b 3 I have no idea what is going on i need help .. could any1 help?
OK, We know from the graph that 12cm3 of aqueous sodium hydroxide was needed to react with 4cm3 of aqueous iron(III) chloride. Because they were all at 1.0 mol/dm3, we therefore realise that 1 mole of aqueous iron (III) chloride reacted with 3 moles of aqueous sodium hydroxide. Therefore, the formula for the precipitate is Fe(OH)3.
For iron (II) chloride, we know the formula of the precipitate to be Fe(OH)2, and so for the same volume of aqueous iron (II) chloride - 4cm3, we know 8cm3 of sodium hydroxide was required. Therefore, you would need to draw the maximum height of the precipitate when volume has reached 8cm3.
Hope this has helped! ;D
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i've got a huge doubttt again :( :( :(
please help ! :P tttthankyou.
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i've got a huge doubttt again :( :( :(
please help ! :P tttthankyou.
D, obviously. Because during the day, the plants photosynthesise, so causing oxygen levels to increase. At night, plants and animals respire so release carbon dioxide, thus reducing the oxygen levels.
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i've got a huge doubttt again :( :( :(
please help ! :P tttthankyou.
Is this chemistry ::) :P
i was about to answer :P
By the way which paper? I mean which session?
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Is this chemistry ::) :P
i was about to answer :P
By the way which paper? I mean which session?
LOLs, Bio in Chem doubts, nicely done there ~VIN1094~! ;D
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UMM.. Honestly no it didnt u answered b 1 when i asked for b2 and 3 but i still dnt get b2 and could u have a look at b3 ..
Thanks :)
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Hi again ..
In may june 08 varient 32 4 a 2 i think ms author has accidently balanced the equation by adding 2 before the H2O
Am i Right?
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UMM.. Honestly no it didnt u answered b 1 when i asked for b2 and 3 but i still dnt get b2 and could u have a look at b3 ..
Thanks :)
That was b)ii). Graph would level off at 8cm3. Explained in the previous post.
OK, We know from the graph that 12cm3 of aqueous sodium hydroxide was needed to react with 4cm3 of aqueous iron(III) chloride. Because they were all at 1.0 mol/dm3, we therefore realise that 1 mole of aqueous iron (III) chloride reacted with 3 moles of aqueous sodium hydroxide. Therefore, the formula for the precipitate is Fe(OH)3.
For iron (II) chloride, we know the formula of the precipitate to be Fe(OH)2, and so for the same volume of aqueous iron (II) chloride - 4cm3, we know 8cm3 of sodium hydroxide was required. Therefore, you would need to draw the maximum height of the precipitate when volume has reached 8cm3.
Hope this has helped! ;D
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Hi again ..
In may june 08 varient 32 4 a 2 i think ms author has accidently balanced the equation by adding 2 before the H2O
Am i Right?
Indeed. the variant 1 mark scheme is right though (doesn't have the 2 in front of it).
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Could someone rexplain please may june 04 q4 b 2 ( i didnt get Ivo's explanation) and b 3 ??
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Indeed. the variant 1 mark scheme is right though (doesn't have the 2 in front of it).
Thanks.
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May june 08 q 8 b 3 the first one my answer was N-H & C=O bonds is it correct & if not what is ?
the second one i dnt quite get what the ms says ??
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May june 08 q 8 b 3 the first one my answer was N-H & C=O bonds is it correct & if not what is ?
the second one i dnt quite get what the ms says ??
Just say:
Similarity: They both have an amide linkage.
Difference: The protein has many different monomers (of amino acids) whereas the synthetic polyamide has only two monomers (dicarboxylic acid and diamine).
I did this paper as a mock and my teacher marked it, full marks for this section.
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Could someone rexplain please may june 04 q4 b 2 ( i didnt get Ivo's explanation) and b 3 ??
What specifically did you not get, I can try and elaborate.
And for iii) The graph would rise to maximum height, then decrease to zero again. Why? Well because aluminium hydroxide (the product formed) dissolves in excess. Think of the test for aluminium cation: add aqueous sodium hydroxide, soluble in excess giving a colourless solution. Same applies here, when a small volume was added, there was precipitate, as you add more and more, it goes colourless, therefore no precipitate. The common mistake is to think of reactivity.
I hope that clears the issue somewhat. :D
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Oh for b 3 that was perfect mate :D
But b 2 the only thing i get is that iron 2 is more reactive period. xD
Could u try and elaborate as u said????
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Just say:
Similarity: They both have an amide linkage.
Difference: The protein has many different monomers (of amino acids) whereas the synthetic polyamide has only two monomers (dicarboxylic acid and diamine).
I did this paper as a mock and my teacher marked it, full marks for this section.
U seem to make it very easy to understand i already have + rep u :D
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Oh for b 3 that was perfect mate :D
But b 2 the only thing i get is that iron 2 is more reactive period. xD
Could u try and elaborate as u said????
What, so you don't get why it's Fe(OH)2?
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What, so you don't get why it's Fe(OH)2?
no i know that its a formula NOT B1 B2 IVO PLEASE WHY DOES IT HAVE TO REACH 8 I MEAN I REAched 7 but i dnt get whats the reason behind that???
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no i know that its a formula NOT B1 B2 IVO PLEASE WHY DOES IT HAVE TO REACH 8 I MEAN I REAched 7 but i dnt get whats the reason behind that???
Just making sure, you're talking about sketching the graph and why the graph reaches 8cm3 maximum height?
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Just making sure, you're talking about sketching the graph and why the graph reaches 8cm3 maximum height?
YES, WHY?:)
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Elaboration::
1) First reaction, FeCl3 + 3 NaOH ---> 3NaCl + Fe(OH)3
so the molar ratio is 1:3 <deduce this ratio by 1)
Second reaction, FeCl2 + 2 NaOH ---> 2NaCl + Fe(OH)2
molar ratio 1:2
so 4 cm3 of FeCl2 reacted fully with 8 cm3 of NaOH
Ivo pls. check!
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YES, WHY?:)
Well, as I explained before. The sodium hydroxide is in excess, so the maximum needed to fully react with the iron(III) chloride is 12cm3. So, simplify the ratio down to 12:4 = 3:1/ So 3 moles of sodium hydroxide reacted with 1 mole of iron(III) chloride. So the balanced equation is:
3NaOH + FeCl3 -> 3NaCl + Fe(OH)3
OK, now if iron (II) chloride:
2NaOH + FeCl2 -> 2NaCl + Fe(OH)2
So 2 moles instead of 3 was required. So if 3 moles was 12cm3, then 1 mole is 4cm3, then 2 moles must be 8cm3. Done! :)
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Elaboration::
1) First reaction, FeCl3 + 3 NaOH ---> 3NaCl + Fe(OH)3
so the molar ratio is 1:3 <deduce this ratio by 1)
Second reaction, FeCl2 + 2 NaOH ---> 2NaCl + Fe(OH)2
molar ratio 1:2
so 4 cm3 of FeCl2 reacted fully with 8 cm3 of NaOH
Ivo pls. check!
Yep, exactly the same!
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THANKS A LOT BOTH :D !
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D, obviously. Because during the day, the plants photosynthesise, so causing oxygen levels to increase. At night, plants and animals respire so release carbon dioxide, thus reducing the oxygen levels.
OH. i thought the q meant O2 was already high in the morning. lol, :s ;S hhaahaaah thaaankyo
Is this chemistry ::) :P
i was about to answer :P
By the way which paper? I mean which session?
LOLLLLL THANKS and sry ::) lol /facepalm. totally posted it in the wrong thread :P :P :P ;D
O/N 06 Bio :P
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some more doubts coming up...............
q4aii),iii)thensame q bii
q6bi its saying ammoniuum ion and ms is giving test abt nitrate ion............
q7b whole
thx in advance........
4) a) ii) Pb(NO3)2 + 2NaCl -> PbCl2 + 2NaNO3
iii) Ag+ + Cl- -> AgCl
b) ii) Please click here (https://studentforums.biz/index.php/topic,8469.msg250425.html#msg250425).
6) b) i) Test: Add aqueous sodium hydroxide. Result: turns damp red litmus paper blue.
7) b) i) Moles of Mg = 3/24 = 0.125
Moles of CH3COOH = 12/60 = 0.200
Using ratios given in the equation, to compare, divide 0.2/2 = 0.100 moles of CH3COOH.
Therefore, magnesium is in excess.
ii) The one not in excess: ie. 0.1
iii) 0.1*24 =2.4dm3
Got it?
Ya got it but q biii u didnt explain
6bi where is this kinda of test mentioned...????
thx a lot..
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Ya got it but q biii u didnt explain
6bi where is this kinda of test mentioned...????
thx a lot..
You mean 6) b) ii) or 7) b) ii)?
And the test for ammonium ions you just need to know. Memorise them!
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I mean 6bii
and u stii havent given ans to 4biii
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Some more doubts
4bi reason
7b again i want a reason.like what was the reaction and all the stuff thx
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Some more doubts
4bi reason
7b again i want a reason.like what was the reaction and all the stuff thx
4B(i) A metal like Sodium or Potassium. Because these metals are from group 1 and 2.
7(b) It would release Nitrogen Dioxide, so it would be a brown gas....
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I mean 6bii
and u stii havent given ans to 4biii
s04
4) b) ii):
Well, as I explained before. The sodium hydroxide is in excess, so the maximum needed to fully react with the iron(III) chloride is 12cm3. So, simplify the ratio down to 12:4 = 3:1/ So 3 moles of sodium hydroxide reacted with 1 mole of iron(III) chloride. So the balanced equation is:
3NaOH + FeCl3 -> 3NaCl + Fe(OH)3
OK, now if iron (II) chloride:
2NaOH + FeCl2 -> 2NaCl + Fe(OH)2
So 2 moles instead of 3 was required. So if 3 moles was 12cm3, then 1 mole is 4cm3, then 2 moles must be 8cm3. Done! :)
4) b) iii):
What specifically did you not get, I can try and elaborate.
And for iii) The graph would rise to maximum height, then decrease to zero again. Why? Well because aluminium hydroxide (the product formed) dissolves in excess. Think of the test for aluminium cation: add aqueous sodium hydroxide, soluble in excess giving a colourless solution. Same applies here, when a small volume was added, there was precipitate, as you add more and more, it goes colourless, therefore no precipitate. The common mistake is to think of reactivity.
I hope that clears the issue somewhat. :D
What don't you get for Q7) b). I thought i made it quite clear. What don't you get?
Any more?
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Some more doubts
4bi reason
7b again i want a reason.like what was the reaction and all the stuff thx
w04?
4) b) i) It would increase because silver is less reactive than tin, so now the difference in reactivity between zinc and silver is greater, therefore the voltage would increase.
Next time, please state which session and year, because I think you're asking me doubts from both s04 and w04, I'm getting confused!
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By the way the more reactive metal is a better reudcing agent becuase it has a greater tendency to form positive ions, whereas the relatively weaker metal is a better oxidising agent as it is the best at accepting electrons.
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hey...
Question 5 b from chemistry may june 2009 variant 1
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7) b) i) Moles of Mg = 3/24 = 0.125
Moles of CH3COOH = 12/60 = 0.200
Using ratios given in the equation, to compare, divide 0.2/2 = 0.100 moles of CH3COOH.
Therefore, magnesium is in excess.
ii) The one not in excess: ie. 0.1
Hey Ivo, can you tell me in detail how did you get the part in bold^^. I'm totally confused with this chapter. Also do you have any rules/notes based on this chapter. Your help is much appreciated! :)
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Hey Ivo, can you tell me in detail how did you get the part in bold^^. I'm totally confused with this chapter. Also do you have any rules/notes based on this chapter. Your help is much appreciated! :)
OK, we know from the equation given, the mole ratio: 1 mole of magnesium reacted with 2 moles of ethanoic acid.
The amounts of substance actually used was: moles of magnesium = 0.125, moles of ethanoic acid = 0.2. But from above, you see the ratio 1:2. So here, we either divide 0.2/2=0.1 or multiply 0.125 by 2 = 0.25.
Either way, you'll find that the magnesium is in excess and the ethanoic acid the limiting reagent. Has this helped?
For the second part, we are also using the mole ratio from the equation where 2 moles of ethanoic acid gives 1 mole of hydrogen. We can't use the calculations for magnesium as this was in excess, so we use the limiting reagent (ie. ethanoic acid), so 0.2/2=0.1.
And no sorry, don't have any notes. I guess, as long as you can handle this question, I think you'll be fine. I don't think it gets any harder than this.
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Also, can someone please explain the colour changes and what happens for the potassium manganate and potassium iodide, I have no idea what they mean. Thanks in advance.
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okay!!! so, we just divide 0.2/2 to get into 1:1 ratio, got it. If yes, then cool +rep. If you say no and start another explanation then imma -rep you >:( .. CHILL just joking ;) Its just that we were never taught such stuff(even if I were I don't remember). THANK YOU SO MUCH IVO, YOU'VE BEEN GREAT HELP! :D
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okay!!! so, we just divide 0.2/2 to get into 1:1 ratio, got it. If yes, then cool +rep. If you say no and start another explanation then imma -rep you >:( .. CHILL just joking ;) Its just that we were never taught such stuff(even if I were I don't remember). THANK YOU SO MUCH IVO, YOU'VE BEEN GREAT HELP! :D
Yep, I guess the top tip for working out limiting reagents and which is in excess is first to convert the substances to moles. Then for comparison, change to 1:1 ratio.
You got it!
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Also, can someone please explain the colour changes and what happens for the potassium manganate and potassium iodide, I have no idea what they mean. Thanks in advance.
Potassium manganate (VII) is an oxidising agent, purple compound. The oxidation state of manganese is +VII. BUt it is much more stable in oxi. state +II. So it is strongly driven to gain electrons and reduce its oxi. state to +II.
So it takes electrons from other substances, in the presence of a little acid. It itself is reduced causing a colour change..
(reduction)
MnO4- ----------> Mn2+
manganate(VII)ion manganese ion(II)
purple colourless
This means KMnO4 can be used to test for a reducing agent.
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Yep, I guess the top tip for working out limiting reagents and which is in excess is first to convert the substances to moles. Then for comparison, change to 1:1 ratio.
You got it!
And buddy you got some rep ;) Thanks again.. :)
About Potassium Iodide, a reducing agent.
H2O2 + 2KI + H2SO4 -----> I2 K2SO4 + 2H2O
H2O2 here is loses O2, therefore reduced. KI helps this to happen also it itself is oxidised to iodine which brings a colour change::
(oxidation)
2I-1 ------------ > I2
colourless brown
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Question:
Products at the electrodes. What's the difference for a dilute aqueous electrolyte and concentrated aqueous electrolyte? Take sodium chloride for example.
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Some more doubts
4bi reason
7b again i want a reason.like what was the reaction and all the stuff thx
w04?
4) b) i) It would increase because silver is less reactive than tin, so now the difference in reactivity between zinc and silver is greater, therefore the voltage would increase.
Next time, please state which session and year, because I think you're asking me doubts from both s04 and w04, I'm getting confused!
and I want reason for 7b u havent explained b4
the paper is attached w04
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Coppe nitrate -> Copper + Nitrogen dioxide + Oxygen
Reddish-brown gas and brown solid will be seen.
-
Question:
Products at the electrodes. What's the difference for a dilute aqueous electrolyte and concentrated aqueous electrolyte? Take sodium chloride for example.
variant one
Ok remember when concentrated NaCl is electrolyzed:
First the solution contains Na+ Cl- and H+ and OH- (from water). The positive inos go to the cathode, and negative ions to the anode.
At the CATHODE
the H+ ions accept electrons, since it is less reactive than Na (always elements which is more reactive 'likes' to stay in the ionic form)
2H+ + 2e- ---> H2
At the ANODE
the Cl- ions give up the electrons more readily than the OH- ions do.
2Cl- --> Cl2 + 2e-
what left in the solution is Na+ and OH- which combine to form NaOH
jus understand the concept ..
(http://content.answers.com/main/content/img/McGrawHill/Encyclopedia/images/CE221700FG0010.gif)
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Question:
Products at the electrodes. What's the difference for a dilute aqueous electrolyte and concentrated aqueous electrolyte? Take sodium chloride for example.
Ok remember when diluteNaCl is electrolyzed:
First the solution contains Na+ Cl- and H+ and OH- (from water). The positive inos go to the cathode, and negative ions to the anode.
At the CATHODE
the H+ ions accept electrons, since it is less reactive than Na (always elements which is more reactive 'likes' to stay in the ionic form)
2H+ + 2e- ---> H2
At the ANODE
the OH- ions give up the electrons more readily as they are in abundance.
4OH- --> O2 + 2H2O + 4e-
what left in the solution is NaCl, which gets concentrated.
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winter 09
question 6 c
how do u do that???
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winter 09
question 6 c
how do u do that???
number of moles of FeSO4 used = 12.16/152 = 0.08
number of moles of Fe2O3 formed = 0.04
mass of one mole of Fe2O3 = 160 g
mass of iron(III) oxide formed = 0.04 × 160 = 6.4 g
number of moles of gases formed = 0.08
volume of sulfur trioxide formed = 0.08 × 24 = 1.92dm3
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did u get it furqan
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yh
i think so
thx vry much!!! ;D
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1.23 g of barium carbonate produces 0.12dm3 [of co2 when treated wid excess hydrochloric acid
calculate the % purity of barium carbonate
thanz if any 1 culd help
:)
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1.23 g of barium carbonate produces 0.12dm3 [of co2 when treated wid excess hydrochloric acid
calculate the % purity of barium carbonate
thanz if any 1 culd help
:)
80%?
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Coppe nitrate -> Copper + Nitrogen dioxide + Oxygen
Reddish-brown gas and brown solid will be seen.
Thx a lot........
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Thx a lot........
its wrong
copper oxide + nitrogen dioxide + oxygeb
blak solid will be seen + brown fumes
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its wrong
copper oxide + nitrogen dioxide + oxygeb
blak solid will be seen + brown fumes
yes
2 Cu(NO3)2 -----> 2 CuO + 4 NO2 + O2
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Sry, my bad.
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Eek, 19 hours left till D :O
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Wat is da structural formula of Germanium oxide?
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https://studentforums.biz/index.php?action=dlattach;topic=1411.0;attach=8470;image
already answered by vin
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It is now known that the smell of the seaside is due to the chemical dimethyl sulfide,
(CH3)2S.
(i) Draw a diagram that shows the arrangement of the valency electrons in one
molecule of this covalent compound.
Use x to represent an electron from a carbon atom.
Use o to represent an electron from a hydrogen atom.
Use ? to represent an electron from a sulfur atom.
i m alwasy confused by this
thanz 4 de help
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https://studentforums.biz/index.php/topic,1411.msg255912.html#msg255912
^^check this
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Can anyone explain in terms of ions and electrons why steel does not rust when covered with zinc. I think I have some misconceptions on this part.
Thanks in advance.
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https://studentforums.biz/index.php/topic,1411.msg255912.html#msg255912
^^check this
thanz n hw wuld do u draw structure of diamond
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Can anyone explain in terms of ions and electrons why steel does not rust when covered with zinc. I think I have some misconceptions on this part.
Thanks in advance.
OK,zinc is welded over iron (in case of a ship). It is more reactive so it gives up e- to form +ve ions more readily. So the zinc dissolves..
2Zn ----> 2Zn2+ + 4e- (oxidation)
The electrons flow to the iron, which passes them on..
O2 + 2H2O + 4e- ---> 4OH-
Adding the incomplete reactions
2Zn + O2 + H2O ----> 2Zn(OH)2
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thanz n hw wuld do u draw structure of diamond
(http://www.chemguide.co.uk/inorganic/period3/diamond.gif)
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Zinc forms positive ions more easily than iron (more reactive), basically it gets oxidized faster in a reaction with oxygen from air to form zinc oxide. When oxidized, it loses electrons (always) to the metal it protects, so iron in this case has a constant supply of electrons, therefore isn`t in a danger of losing them. The same is with cathodic protection in which electricity connected to the metal supplies it with electrons... Basically preventing the metal to form positive ions, aka, give electrons away... I hope this explanation is sufficient ;)
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Thanks VIN and TLI~
-
also, plz, when a gas is collected from a reaction, why does it have to pass through a liquid, and then finally be collected, and what role does the type of a liquid play in all this? Help, plz, don`t get it...
:)
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Anyone?... Pretty please?
-
also, plz, when a gas is collected from a reaction, why does it have to pass through a liquid, and then finally be collected, and what role does the type of a liquid play in all this? Help, plz, don`t get it...
:)
Er, I don't really know the exact reason but a gas is collected over because it is insoluble in water and it is more convenient. Sorry I couldn't help you much. i would be waiting for an accurate answer too. :-[
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Thanks anyway! You know what I mean though, right? For example in catalytic cracking, when an alkene is collected, the delivery tube first passes through water... why? Why not just downward delivery? That`s just an example though, there are other reactions involving another liquid, not water...
Anyway, good luck!
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http://www.xtremepapers.net/CIE/Cambridge%20IGCSE/0620%20-%20Chemistry/0620_w09_qp_31.pdf
5c(ii) can ny 1 help wid de equation
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Please can somone answer my doubtful doubt! :P
For varying concentrations of acid in reactions and looking at rates, why sometimes when they sketch a graph, increasing the concentration of acid still has same amount of product (gas) produced, but other times, when double concentration, the gas volume doubles?
Majorly confused. How about with surface area and temperature, do they have an effect on the final amount of gas produced?
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http://www.xtremepapers.net/CIE/Cambridge%20IGCSE/0620%20-%20Chemistry/0620_w09_qp_31.pdf
5c(ii) can ny 1 help wid de equation
4
OK, Ge4H10 is like any other Alkane which forms CO2 and water.. but it this case its GeO2
Complete combustion
C4H10 + 13 O2 --> 4CO2 + 5H2O
Ge4H10 + 13 O2----> 4 GeO2+ 5H2O
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Please can somone answer my doubtful doubt! :P
For varying concentrations of acid in reactions and looking at rates, why sometimes when they sketch a graph, increasing the concentration of acid still has same amount of product (gas) produced, but other times, when double concentration, the gas volume doubles?
Majorly confused. How about with surface area and temperature, do they have an effect on the final amount of gas produced?
OK, I get a part of your ques. Is this what you are looking for?..
Zn + 2HCl ---> ZnCl2 + H2
Conc. for acid doubled, but same amount of Zn used reaction faster but results in same volume of H2 gas.
Doubling the amount of both reactants results in doubling of product (gas).
Surface area and Temperature doesn't have anything to do with the yield, they only influenced the rate of reaction. Posting a q. as an example would do good as I still cannot properly get your question. Usually in the ques it is mentioned right, when the conc of reactants in increased/decreased.
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OK, I get a part of your ques. Is this what you are looking for?..
Zn + 2HCl ---> ZnCl2 + H2
Conc. for acid doubled, but same amount of Zn used reaction faster but results in same volume of H2 gas.
Doubling the amount of both reactants results in doubling of product (gas).
Surface area and Temperature doesn't have anything to do with the yield, they only influenced the rate of reaction. Posting a q. as an example would do good as I still cannot properly get your question. Usually in the ques it is mentioned right, when the conc of reactants in increased/decreased.
Hmm, I'm still a bit confused. Maybe a question example might help. w02, Q2) c) ii) and iii)
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Hmm, I'm still a bit confused. Maybe a question example might help. w02, Q2) c) ii) and iii)
OK here, look at the reaction. Its the decomp. of H2O2. Doubling the conc. of H2O2 increases the amount of oxygen in H2O2 by twice. Hence when
it reacts with H2O2 decomposes there is now twice the number of O2 produced.. got it?
Also when amount of catalyst is halved the reaction is slower. As you know a catalyst never takes part in a reaction so it really doesn't affect the amount of O2 produced.
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OK here, look at the reaction. Its the decomp. of H2O2. Doubling the conc. of H2O2 increases the amount of oxygen in H2O2 by twice. Hence when
it reacts with H2O2 decomposes there is now twice the number of O2 produced.. got it?
Also when amount of catalyst is halved the reaction is slower. As you know a catalyst never takes part in a reaction so it really doesn't affect the amount of O2 produced.
OK, I kinda got it. So for this example, increasing the concentration means increasing the amount of hydrogen peroxide dissolved in the water, so if there is double the the amount of hydrogen peroxide dissolved, then double volume of oxygen produced and in faster time.
However, would this be the same for excess. Say sodium hydroxide reacted with hydrochloric acid. Hydrochloric acid was used as the excess, would doubling the concentration of acid also double the amount of sodium chloride? If not, why?
And is it true that increasing the volume of something decreases the rate?
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OK, I kinda got it. So for this example, increasing the concentration means increasing the amount of hydrogen peroxide dissolved in the water, so if there is double the the amount of hydrogen peroxide dissolved, then double volume of oxygen produced and in faster time.
However, would this be the same for excess. Say sodium hydroxide reacted with hydrochloric acid. Hydrochloric acid was used as the excess, would doubling the concentration of acid also double the amount of sodium chloride? If not, why?
And is it true that increasing the volume of something decreases the rate?
I guess you are mixing up two concepts. If you add excess HCl ALL the NaOH would be reacted BUT this doesn't mean that it always doubles the amount of NaCl. This depends on how much NaCl is present.
Yes, increasing the vol. decreases the rate as you've added more molecules to be reacted and this would take more time.
Anyway I'm off now its 4:30 am!
GOOD LUCK! :D
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Potassium manganate (VII) is an oxidising agent, purple compound. The oxidation state of manganese is +VII. BUt it is much more stable in oxi. state +II. So it is strongly driven to gain electrons and reduce its oxi. state to +II.
So it takes electrons from other substances, in the presence of a little acid. It itself is reduced causing a colour change..
(reduction)
MnO4- ----------> Mn2+
manganate(VII)ion manganese ion(II)
purple colourless
This means KMnO4 can be used to test for a reducing agent.
Just one more thing, here you said potassium manganate is an oxidising agent. So does that mean when it oxidises something, it changes from purple to colourless? So what do you mean by test for a reductant? You mean when the other thing reduces the potassium manganate, the colour changes or what?
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Just one more thing, here you said potassium manganate is an oxidising agent. So does that mean when it oxidises something, it changes from purple to colourless? So what do you mean by test for a reductant? You mean when the other thing reduces the potassium manganate, the colour changes or what?
You'll also be rewarded for your hard work by me +repping you like a million times! :D
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Just one more thing, here you said potassium manganate is an oxidising agent. So does that mean when it oxidises something, it changes from purple to colourless? So what do you mean by test for a reductant? You mean when the other thing reduces the potassium manganate, the colour changes or what?
This is right..w09 paper, Q 6 a) b) ii) talks about this.
Also an oxidising agent brings about oxidation if another substance and itself reduces. vise versa for reducing agent.
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This is right..w09 paper, some q. talks about this.
Thanks for all your help. I have added the reputation, and a very long comment! Enjoy reading it, or shall I say enjoy your good night's sleep! Wow, 4am, you better go!
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On which bases can we determine that a metal would react with dilute HCL?
-
2 questions,
1st, there was a qs in stoichiometry and the answer was that there were 0.03 moles of O2 molecules then they asked how many moles of oxygen atoms will there be. the answer is 0.06. i dont get why :/ isnt it supposed to be the opposite? like you half it instead of twice it? :/
and second question, in CO2 are the C and the O bonded by a double bond? cuz if theres only a single bond then there are only gonna be 6 e's around C
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On which bases can we determine that a metal would react with dilute HCL?
Reacts with metals which are higher than hydrogen in the reactivity series.
(http://www.frankswebspace.org.uk/ScienceAndMaths/chemistry/reactivitySeries_Files/reactivitySeries.gif)
^^Why? Because a metal lower than hydrogen (Copper/Silver/Gold/Platinum) wont be able to displace H2 from HCl
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Right, thanks a lot!
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2 questions,
1st, there was a qs in stoichiometry and the answer was that there were 0.03 moles of O2 molecules then they asked how many moles of oxygen atoms will there be. the answer is 0.06. i dont get why :/ isnt it supposed to be the opposite? like you half it instead of twice it? :/
and second question, in CO2 are the C and the O bonded by a double bond? cuz if theres only a single bond then there are only gonna be 6 e's around C
Where was the question? I need it, other wise wont be able to solve..
Yes, double bond..
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Where was the question? I need it, other wise wont be able to solve..
Yes, double bond..
thank you thank you thank you! :D
its question 2)c) O/N 01
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As all IGCSE chemistry exams are over this thread will be now locked.