IGCSE/GCSE/O & A Level/IB/University Student Forum
Qualification => Subject Doubts => IGCSE/ GCSE => Sciences => Topic started by: Naruto on May 01, 2009, 02:33:53 pm
-
hello
Can anyone tell me how to make an ionic equation?
And what will be the ionic equation of the following:-
1) 2NaOH + H2SO4 ---> Na2SO4 + 2H2O
2) CuSO4(aq) +2NaOH(aq) ---> Cu(OH)2(s) + Na2SO4(aq)
3) MgCO3 + H2SO4 ---> MgSO4 + H2O + CO2
-
if its an alkali reacting with strong acid the ionic equation will be
OH(negative)+H(positive)-----> H2O
this one is for the first one
im not sure about the rest , but here is one more thing
ionic equation for any ammonium salt reacting with alkali is -->
NH4(+) + OH(-) -----> NH3+H2O
-
Thanks emi :) so you mean that for a particular reaction ( like acid reacting with metal) the ionic equation will always be the same.. no matter what the reactants are?
And can anyone help me out with the rest of the equations and tell me the way to work out the ionic equation... i would be grateful.
Thanx
-
im not so sure of ammonium and alkali...
hm...
-
yes for strong alkali + strong Acid the ionic Equation will always be the same which is
OH(negative)+H(positive)-----> H2O
same goes for the ammonium salts reacting with alkali
NH4(+) + OH(-) -----> NH3+H2O
-
in inoic equation take only that change state OR thier bondinfg
1.OH(-)+H(+)=H2O
2.Cu(2+)+OH(-)=Cu(OH)2
3.2H(+)+CO3(2-)=H20+CO2
-
@ hyebyekadal
Can you tell me that why in your answer to number 3 there are 2H+ ions????
plzzzz tell me bcuz this was the main reason why i wrote these equations...
-
Okay hyebyekadal is not online so can anyone else tell me...plzzzzz :(
-
The equations have to balance for the charges. In equation 2 there should be 2 OH(-)
-
If we have to balance it then why in equation 1 its not 2H+?
-
1 - cancels 1+
-
ummm...i thought that bcuz there are 2 hydrogen atoms on left side and 2 on right side thats why its not 2H+?
OH- + H+ ---> H2O
-
yup, what you just said is right!
-
hey guyz thanks for answering my question it had cleared my confusion, but i have some for question....hope you will answer them in a same way:)
Q: which is more accurate 'burette' or 'pipette' or 'measuring cylinder' ?
Q: What is the maximum range of all these three insturments?
Q: And sometime in the exam they give us a situation like..... '25 cm3 of acid is used, so which insrtument will be used to give an accurate measurement?
thanx:):)
-
lol i need help in that too but i no pipette more acccurat thatn measuring cylinder.. also
OUt of this topic sorry but can anyone whos really good at IGCSE physics tell me how to prepare for p6??
I mean we never did like any experiment at school. Because um.. my teach is ,,um ahem//
nvm so can anyone tell me any good other site or something? my 1rst exam is p6 phy and on may 12th.
i hv study guide and tom duncan IGCSE phy...
so Thank You in advance!
-
normally, a pipette is only used for a few drops of a solution. A biuret is bigger and it can range from 10cm3 to 50 at the max. However whenever the quantity of the solution u r measuring is above 20cm3 it is advisable to put it in a measuring cylinder.
-
@godfather
thanx for your help, itz really helpful... but are you sure about your answer ;) No offence!!! :)
@everyone
hey guyz i have one more question about fizzy drinks....
well there was a question in year nov 2001 last question ( i have attached the link)
so can you tell me from which topic was this question from?
and can anyone explain me the part (c)??
Thanks.
-
i need the answer...plzzzzzzzzzzzzzz i have a test tomorrow :'(
help me :(
-
I will be able to answer this in 90 mins. Now i am on a mobile phone.
-
okay no prob...i will wait
-
Fill a large basin full of water. Invert another basin and completely submerge it in the first one so that it is full of water with no air bubbles. Now put the can of coke unside the upturned submerged 2nd basin and open it. The volume of gas releaSED is the answer. This can be found by using a calibrated beaker as the upturned 2nd container.
-
astar i didnt get what u mean..
sorry and i looked up the ms and its undecipherable!
can open under water to collect gas in graduated tube / m. cylinder (1)
filled with water (1), syringe = 0 (would not work) [2]
-
fill a beaker or a measuring cylinder with water to the brim. place it in another bowl full of water but turn it upside down inside the water without letting the air bubbles get in. submerge the can under the water and place it under the beaker/measuring cylinder (make sure no air bubbles get in and the beaker covers the top portion of the can only). open the can and when the gas bubbles are released, it is trapped by the measuring cylinder and gas replaces the water inside the measuring cylinder. take the reading of the empty space inside the measuring cylinder. that is the volume of the gas released.
-
@astar & godfather
thanx guyz for your help that question really confused me especially the mark scheme.....
and if im not wrong i think this method is called the downward displacement of water...right?
-
yes, good luck! ;)
-
Thank You but isnt CO2 heavier than air? so how the gas would still form on top of water??/ ( ok i hve a feeling i kinda mixed up concepts but ...)
-
there is no air inside the beaker because it is filled with water
-
hey guyz i have one more question....
Q: what is haxane layer colour??? well i dont know what is this word haxane layer means???
so plzz do answer me!!
Thank U!!! :)
-
hey guyz i have one more question....
Q: what is haxane layer colour??? well i dont know what is this word haxane layer means???
so plzz do answer me!!
Thank U!!! :)
the colour of hexane layer depends on the halogen produced during the reaction
check out these sites
http://www.miracosta.cc.ca.us/home/dlr/110exp10.htm
http://jchemed.chem.wisc.edu/jcesoft/CCA/CCA3/MAIN/HALOGEN/PAGE1.HTM
-
@ twilight
thanx that site really helped me!!! :)
-
Okay should i study Extraction of metal for paper6? i mean does this topic ever come in paper 6??
-
Okay should i study Extraction of metal for paper6? i mean does this topic ever come in paper 6??
Naruto it rarely comes in paper 6 all the questions about extraction comes in paper 3 and paper1
-
So did it ever came in any year?? If you know plzz tell me.
-
hey... why is no one here like a* material...
what the guys said before me is wrong.
i mean the ionic equations, and what to use for measurements (i havent seen the question u posted in the attachment yet, but when i do, another rant)
to write ionic equations, you first have to understand what they are. basicly all they do is split up every single compound that is reacting into what it really is(eg NaOH(aq)=Na+ and OH-) (this is because when something dissolves in water, it splits up into ions)
when you have done that, you must cancel out all "spectator" ions. this means that any ions which appear on both sides of the equation must be crossed out. (remember covalent compounds arent made of ions, and only aqueous compounds can be split up into ions)
eg
NaOH(aq) + H2SO4(aq) ----> NaSO4 (aq) + H2O (l)
change into ions...
Na+ + OH- + 2H+ + SO42- ---> Na+ + SO42- + H2O
Now simply cancel out all spectator ions (any that are not taking part in the reaction) to give:
Na+ + OH- + 2H+ + SO42- ---> Na+ + SO42- + H2O
and so
2H+ (aq) + OH- (aq) ---> H2O (l)
the state symbols are simply the state symbols of the original reaction (remember, putting in state symbols is one of the best ways to impress the examiner, even if they aren't required!)
ok, now the measuring part.
i assume 25cm3 is meant for a titration. the best way to accurately measure a fixed volume of liquid is always to use a volumetric pipette (as in if you need 15cm3 to add to something, not to measure the volume of for example the reactant produced in a reaction). in igcse at least. a beaker and a measuring cylinder are used only to estimate the volume of a liquid.
to measure constantly changing volumes of liquid, the best is of course a burette. this for us is mainly in titrations, i doubt you would use it anywhere else. a pipette is not used to ever measure anything-volumetric pipettes are though. you cannot call a volumetric pipette a pipette in your exam, or else you'd probably get it wrong.
some stuff about pipettes:
http://www.chem.yorku.ca/courses/chem1000/equipment/pipette.html
regular pipettes (aka dropper, dropping pipette (best name), teat pipette) are used for transferring small amounts of liquid, eg indicator.
until now no question in igcse chemistry extended has asked for measurements of a substance, eg volume of liquid obtained from experiment. and they probably wont. if they do, the best way to measure is a measuring cylinder. (remember to try to avoid this as much as possible, and mention how inaccurate it is when you do write up an answer)
hmm... what else... its so sad you guys dont have a good chemistry teacher. you wont be able to do the whole syllabus properly in even a month of constant study without a good teacher. what does a good teacher do? make sure you dont do too much outside the syllabus, and make sure you know everything in the syllabus.
ok whatever bye.
-
@unown.xu
ur great :) and thanks a lot for answering my questions.
-
wow you're welcome... hope i can help in the future...
@admin (i thnk astarmathandphysics):
the papers don't load properly almost ever! i have no idea why-ive enabled popups and all, but it just stops in the middle usualy. 1/10 times itll work, usually it doesnt... ive tried downloading it, but it never works (everytime i refresh, it either is completely fine, asks me the answer to a question so im not a bot, or outright denies access). i use firefox 3, vista. the papers sometime even get corrupted while im downloading them-i think you have just way too much traffic. why dont you use a free host and backup all your files there, so that you get less traffic and your site is more reliable? maybe rapidshare? make an account, you'll get loads of downloads... or maybe multiple free accounts on blackapplehost. i dont know. your choice... but please fix the problem...
-
hey guyz i have one more question....
Q: what is haxane layer colour??? well i dont know what is this word haxane layer means???
so plzz do answer me!!
Thank U!!! :)
is this there for igcse?
-
Thank You unown.xu even u said my ans was rong! but according y textbook and teach speatator ions are ions that
1.dont change the state
2.dont change their bonding
and that actually works uno tahts how i got a lot of em and true ill alwasy check with syllabus and find that stuff in text not there in syllabuus! like for in gum disease is NOT required and i hve benn studying it for a long time !
-
can somebody please help me with this question
question 4 0620_s08_qp_6 (especially, i don't get the 0.0cm3 part.
Thanks in advance :D
-
Can you please put the link for the question and the number of it?
-
is organic chemistry coming in paper 6 ??
what els topics that are not likely to come ?
-
can somebody please help me with this question
question 4 0620_s08_qp_6 (especially, i don't get the 0.0cm3 part.
Thanks in advance :D
I cant find the 0.0cm3 part
-
here's the link to the question
http://www.planet-master.com/Cambridge_IGCSE/0620_S08_qp_6.pdf
It's question number 4
Thanks
-
k i get wut u mean
the 0.0 cm3 is the highest marking in th biurette .. bcoz a biurette is marked with from top to bottom
so here it means tht the biurette is filled to the highest marking
-
roughly its like this . i've attached a rough drawing of the markings
-
guys need help
from oct 2008 2(c)
Suggest why bubbles of gas were not seen immediately in 2.
And the ms says gas dissolves in water. So the gas formed I.e. chlorine dissolves in water??
-
guys need help
from oct 2008 2(c)
Suggest why bubbles of gas were not seen immediately in 2.
And the ms says gas dissolves in water. So the gas formed I.e. chlorine dissolves in water??
ya i really also want to know
-
well i answered using that answer without understanding it actually.....but there is another REASONABLE answer
Chlorine in a heavy gas (or slightly heavy)...so it took sometime before rising up
-
The motion of chlorine ions towards the electron is almost random, and each time the hit a molecule they are knocled back and accelerate 35 times slower than hydrogen ions because they are 35 times heavier. Hence on average their speed will be much slower and they will take longer to get to the electrodes.
-
astarmathsandphysics and sanity_master=ur answers are perfect but it's not included in marking scheme. Will we get it wrong if we wrote it?? ???
-
They say suggest a reason so you will get the marks.
-
in a suggestion question....u will get the mark if the reason is rational :)
so u can answer about being heavy and slow and about dissolving
-
Can anyonw tell me
What are antibumping granules? and why are they used in simple distillation?
-
they are kinda like boiling chips ... they are used to make the boiling of the sol. smooth .. not to allow the sol. to over heat or super heat that kinda thing :D
-
yup xactly .. and to prevent the chemicals from splashing as they might be harmful
-
Pipette is the most accurate of them all and i think a buerette should be needed for measuring ACID and pipette can also be used.
Measuring cylinder is not used as the range is very small.
-
electrolysis of concentrated sodium chloride using carbon electrodes
the solution also contained litmus solution
What happened to the colour of solution around cathode
Why did this change take place?
If there is hydorgen produced at the cathode
then why would there be a colour change since hydrogen is a neutral gas...shouldnt it stay green?
I dont get it...
-
the solution is concentrated i.e. very less water molecules are present
so it is sodium ions that go to the cathode .. not hydrogen bcoz hydrogen is not abundant enough in the solution
-
you are wrong twilight in electrolysis the cation which is lower in the reactivity series i.e. hydrogen
concentration only effects which anion goes i.e. chlorine
when chlorine and hydrogen leave sodium hydroxide is left behind which is a base so litmus indicator turns blue.
-
ur right yinyang!
-
electrolysis of concentrated sodium chloride using carbon electrodes
the solution also contained litmus solution
What happened to the colour of solution around cathode
Why did this change take place?
If there is hydorgen produced at the cathode
then why would there be a colour change since hydrogen is a neutral gas...shouldnt it stay green?
I dont get it...
Chlorine and hydrogen leaves .. NaOH is left in the solution turning theu niversal indicator blue cause its a base and chlorine bleaches
-
you are wrong twilight in electrolysis the cation which is lower in the reactivity series i.e. hydrogen
concentration only effects which anion goes i.e. chlorine
when chlorine and hydrogen leave sodium hydroxide is left behind which is a base so litmus indicator turns blue.
sorry . :-[ my wrong
-
Guyz plzz help me out with the last question of chemistry paper6 Nov 2000
plzzzz explain the full answer because it is of 6 marks...and tell me this question is from which topic?
i have attached the link
Thanks
-
Would it simply be that no more is formed?
I know nothing about chenistry but I find exam questions very predictable.
-
ummm...astar are you answering my question :-\
its the question no. 6 on the last page...about calcium carbonate
i think you checked the wrong question...but its ok you can check and tell me if you knw the answer.
thanks
-
ummm...astar are you answering my question :-\
its the question no. 6 on the last page...about calcium carbonate
i think you checked the wrong question...but its ok you can check and tell me if you knw the answer.
thankshttp://www.mozdev.org/
My browser is behaving strangely but are you saying?
Calcium carbonate is found in egg shells. All carbonates react with hydrochloric acid to form
chlorides. Calcium carbonate is insoluble in water but calcium chloride is soluble. Most impurities
in egg shells are insoluble. Plan an experiment to find out if egg shells are 100% calcium
carbonate.
-
k i think u havta put the eggshells in HCl (CaCO3 will react to give CaCl2).. after the reaction .. add water to dissolve the CaCl2 that is formed .. and filter the mixture .. if there is any residue in the filter paper then the eggsells are not 100% .. as only CaCl2 dissolves in water
-
@ astar
yeah i am asking for that question
@ twilight
Thanks for your answer
-
Ok need help winter 2005 IGCSE
5 A solid compound X was analysed. Solid X was an aluminium salt. The tests on X and
some of the observations are in the following table.
Complete the observations in the table.
(a) One spatula measure of X was
placed into a hard-glass testtube.
The solid was heated
gently then strongly. The gas
was tested with pH indicator
paper. paper went red
ms sayss acidic gas/hydrated
and the theres a quesiton about the the substance x and the ms again says a hydrated salt.
if its a hydrated salt then why acidic gas forming?
-
there must be something mentioned above in the question so that they can say hydrated ... maybe it was heated and it gave out h20 vapours ...
the answer is hydrated acid salt ... i think
-
here's a link through which anyone can learn the anion and cation tests easily.
http://library.thinkquest.org/2923/tests.html
-
this is whole q!
-
5 A solid compound X was analysed. Solid X was an aluminium salt. The tests on X and
some of the observations are in the following table.
Complete the observations in the table.
(a) One spatula measure of X was
placed into a hard-glass testtube.
The solid was heated
gently then strongly. The gas
was tested with pH indicator
paper. paper went red
The salt was probably aluminum carbonate which decomposed on heating to aluminum oxide and carbon dioxide. Carbon dioxide is acidic so the litmus turned red.
-
o no i thought of that also but the later in the question u find out its nitrate and there NO mention of carbonate thats what i wrote! I said that there were carbonates impurities.. but the only answer the ms provided is hydrated salt!
-
Why don't you post the entire question. maybe we could help you better then.
-
atttached paper Q5
-
water droplets came from the solid X .... hence the water on the top of the test tube .... hence its hydrated
-
what i don't understand in the question is how is the salt a nitrate? (according to ms)
-
water is not acidic is it?? then why does ph indicator show RED??/
also ms for the q is acidic gas..
-
Nitrogen oxide is produced on heating which is acidic. Thus, litmus goes red.
-
thanks a lot pharoah!
but how come the ammonia is also released?
-
why is ammonia produced?
o god learn you anion tests!!!!!!!!!!
because you add Al foil and make alkali with sodium hydroxde!! see last part of question!!!!!
and pharoah I think you are right but what's that go to do with hydrated salt?? that's what it says in ms!!
-
I THINK I DO KNOW MY ANION TESTS! >:(
I'm just asking how is it possible that both an acidic and alkaline gas is produced.
-
kk chill!
-
all cool!! ;D ;D
-
hey..i also need phy notes...n if anyone can get me business IT biology chemistry...it would be a great help..thanx... :)
-
why is ammonia produced?
o god learn you anion tests!!!!!!!!!!
because you add Al foil and make alkali with sodium hydroxde!! see last part of question!!!!!
and pharoah I think you are right but what's that go to do with hydrated salt?? that's what it says in ms!!
Evidence for it being a hydrated salt comes from the condensation at the top of the tube. When the salt is heated, water is converted into steam which again condenses to water on the cooler upper parts of the test tube. If it was not a hydrated salt, the condensation would not take place.
-
if we only heat, wouldnt there be steam on the test tube that would be called condensation?
or is it the condensation that occurs after heating has been stopped?
-
Condensation will occur on any cool surface. It doesn't matter whether heating is going on or not since glass is a very poor conductor of heat but more condensation will occur when heating is stopped as the surfaces get cooler.
-
thanx for the info.
+rep
-
Thank you! My first rep gain! :D
-
thanx man ur first one to clearly exaplin and come back and help out again Thank You again !
PS. i also plus repped you ! check it out!
-
if we only heat, wouldnt there be steam on the test tube that would be called condensation?
or is it the condensation that occurs after heating has been stopped?
no no no! this is how examiners can tell which centres dont do practicals with their students. have you ever tried to heat a hydrated salt? in lab? (i havent either but ive seen a vid lol)
what happens is that "water condenses on the cooler upper regions of the test tube". even while you're heating.
<half an hour later>
ive been looking for a video to show u for the past half hour, but i cant find any. really sorry. dont bother checking youtubbe or metacafe-i checked both. whatver... do it at home maybe... if u have a test tube and hydrated copper (II) sulphate crystals. lol... maybe you could make some other crystals? (most ionic compounds' crystals are hydrated)
-
@ unown.xu
hey dude can you tell me the answer to my question about those egg shells...its from the year Nov 2000 paper 6...i would be gratefull to you.
Thanks in advance
i have attached the link to that question
It is the last question, page number 12 and about the egg shells
-
hey guyz!! well i have a confusion for paper 6... i am confused about some chapter/topic that should i study them for paper 6 or not. Those topics are like (Mole, Atomic Structures, Ionic & Covalent Bond, Stiochiometry and esters)
thanx :)
-
paper 6 only includes the topics from the core content. so petrochemicals and polymers is not at all going tome. Basics on mole can possible come. you need to know the covalent and ionic bonding because it is the basics of chemistry.
-
hey dude can you tell me the answer to my question about those egg shells...its from the year Nov 2000 paper 6...i would be gratefull to you.
Thanks in advance
Ok. First you have to react it with HCl. Then filter the solution. The solution will contain CaCl2 which is soluble. If any impurities are present they will appear as residue. Now the ques is for 6 marks so you should put in practical details like use measuring cylinder to add 5 cm3 of HCl and wait till production of effervescence stops before fitering to ensure that all CaCO3 has reacted and the moles of HCl used must be at least double that of the egg shell . And use filter paper and funnel to filter. wet the filter paper so that it becomes easier to filter. Also the filtrate can be left to evaporate and the crystals that are firmed can be observed. If only CaCl2 is present, pure crystals will be present.
Also, the reaction between CaCO3 and HCl is exothermic so you need a test tube holder and have to be careful not to burn yourself. And HCl is corrosive-care required.
-
thanx man ur first one to clearly exaplin and come back and help out again Thank You again !
PS. i also plus repped you ! check it out!
Thanks dude! I do what I can. Glad to be of assistance :)
-
hey...Can you guyz tell me that in chem paper6 when they ask us to draw a smooth line graph do we have to draw it with the help of ruler or without it... i mean like we make a smooth curve
@unown.xu
Thanks a lottt!!!! ;D
-
Anyone plzzz tell me i have been waiting for a long time :( im solving a past paper where im supposed to draw a smooth line graph so plzzz tell me i have to solve so many papers :(
-
u have to do it wid a free hand no ruler
-
which paper r u doing? i need to know the question to answer your question.
-
which paper r u doing? i need to know the question to answer your question.
u dont need to know the question because smooth curve alwayz means free hand no ruler
-
u have to do it wid a free hand no ruler
depends on the question cause i just did a very similar question and it asked me to draw a smooth line graph. Turns out i had to draw a straight line with a ruler
-
but i have heard frm my teacher for smooth line they give marks for widout ruler
-
but there are more chances of you being right cause according to what Naruto said, he said smooth line curve.
Anyways :D
-
lol jus check wid the ms n we'll get it ;D
-
thas why i asked for the question paper. :)
-
Extremely sorry by mistake i wrote smooth line curve
actually i wanted to know about smooth line graph
and im doing may/june 2001, question 3 and 5
thanks
-
ahhh now that changes things. it can be either a curve or a straight line.
I'll check it and tell you in a minute
-
i just realised i don't have those papers. Could u upload them?
-
well when they say smooth line u do it free hand
straight line --- wid ruler
best fit --- wid ruler
-
but when they say smooth line graph, it can be either. I just did the 2003 past paper and i encountered 2 graphs having the exact wording "smooth line graph", one turned out to be a straight line while the other one was curved.
-
oook i have 2001 n the answer here issssssss q3 is curve n q5 is a straight line according to wt i did which is checked :D
-
i told you it can be either one! ;)
-
yeah exactly mostly the wording is smooth line graph...so how can we decide wat to do
like in may/june 2000 it was smooth line graph and i made it a straight line
so this is really confusing...wat to do :-\
-
Well i dont think it can be either because in the markscheme it is always mentioned wat type of graph should be drawn
-
in may june 2000 its a curve no ruler i think if they mention smooth it means u dnt have to use a ruler as mentioned in may june 2001 q 5 it only says draw a graph of these results so i used a ruler whereas in q3 they mentioned smooth line......
-
In chemistry, when plotting a graph of reaction rate, you must draw a curve of best fit through your prints. Lines drawn with a ruler from point to point will not get a mark
this is frm the examiners tips for chem ..... its there in the topic revision checklist
-
basically when the question has something to do with reaction rate (for example a graph showing the volume of oxygen collected over time taken), the graph will be a curve because every reaction starts, continues for a while, slows down and then stops. a straight line is drawn either for scatter graphs (definitely) or for some line graphs (where time is not one of the variables).
-
Does anyone know where I can get IGCSE Chemistry May/June 2008 Paper 6 from ?
The don't seem to have it on any site .... ???
and I need it Urgently..!!
Thanks
-
babes ull find them in www.freeexampapers.com or in www.xtremepapers.com
knock ur self out :D
-
hey can anyone help me with the following question
This is the last question of Oct/Nov 2002 paper6 about the sloubility
in the mark scheme it is written that "work out the solubility"...so do i have to write the method by which i can find the solubility or just this statement ???
plzzz tell me wat will be answer...i will appreciate if anyone give me a whole answer to this question.
Thanks
i have attached the mark scheme and the question paper, it is the question no. 7
-
the examiner expects you to write the method of working out the solubility (it's better because you are telling the examiner that you know what you are doing). It's the original mass - the residue mass .