IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: aldehyde1612 on May 17, 2010, 04:54:05 pm

Title: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: aldehyde1612 on May 17, 2010, 04:54:05 pm: iv got CIE paper3 varient 3.. i think.. on wednesday.
Anyone got any tips... advice? ;D

AND apparently there arent any titrations this year.... ???
is that even possible.?
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: AS-Girl on May 17, 2010, 05:31:46 pm: Quote from: aldehyde1612 on May 17, 2010, 04:54:05 pm
iv got CIE paper3 varient 3.. i think.. on wednesday.
Anyone got any tips... advice? ;D

AND apparently there arent any titrations this year.... ???
is that even possible.?

on wednesday...thats weird..i have my exam on thursday!!
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: Candela on May 17, 2010, 06:07:39 pm: thts weird!! .....yup me 2....i hav it on thursday!
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: ifraha18 on May 17, 2010, 09:27:04 pm: mines on 20th thrsdaii
cant the wednsdai ppl tel us den.????
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: Candela on May 17, 2010, 10:19:32 pm: Quote from: ifraha18 on May 17, 2010, 09:27:04 pm
mines on 20th thrsdaii
cant the wednsdai ppl tel us den.????
lol...bt tht clearly means...our pprs wud be different! :)
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: ifraha18 on May 18, 2010, 12:24:15 am: if its variant 3 den its same all over the world
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: matabd on May 18, 2010, 09:14:33 am: Well the best advice available is to just follow the instructions really .
Cos they explain everything really well.
Also read up on your existing reports, eg. calculations and all that.
Also when your doing salt analysis, always look at the Salt Analysis note at the end of the paper. And try to rule out as many ions that you can
Good Luck !
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: aldehyde1612 on May 18, 2010, 10:37:30 am: Quote from: AS-Girl on May 17, 2010, 05:31:46 pm
on wednesday...thats weird..i have my exam on thursday!!

oh. whoops. :P yeah i got it on thursday... my week started with the bio practical.. which was today (tuesday) not monday. lol.

but have u guys heard anything about there being no titrations... ???
cause if incase there isnt... what could there be instead?...:-\ enthalpy stuff like heats of neutralisation?
and theres the cations and anions identification yeah?
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: matabd on May 18, 2010, 11:47:26 am: haha . . .no man . . cant imagine no tirations :) but its likely, you could also get Heat change, Water of crystallization stuff . . . Uhmmm i guess thats basically it.
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: marolareine on May 18, 2010, 04:53:24 pm: i did hear from some ppl that there would be no titration too and there would be an enthalpy change question instead..i guess..
..am doing paper 33
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: superduper2009 on May 18, 2010, 05:22:37 pm: How do u do the exp. for water of crystallization ????
and what are the tests that we have to know apart from the ones that they give on the last page....
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: aldehyde1612 on May 18, 2010, 05:36:09 pm: Quote from: superduper2009 on May 18, 2010, 05:22:37 pm
How do u do the exp. for water of crystallization ????
and what are the tests that we have to know apart from the ones that they give on the last page....

ooh. good question... we havent really done anything other than titrations in school. :-\

and i guess for the tests... they wouldnt give you ones that arnt there.
but you might need to know what you're supposed to add to neutralise a solution - like whether to use nitic acid or HCL?? and remember formulas maybe??... and how to differentiate between ones that give similar results. but i think something about Al and Pb is given on the sheet too.
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: sabrina on May 19, 2010, 09:16:26 am: hi guys
anyone with tips to how to solve mole questions. those r very hard or me. n anyone have any idea as what can be asked. thanks in advance
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: AS-Girl on May 19, 2010, 10:52:43 am: Quote from: sabrina on May 19, 2010, 09:16:26 am
hi guys
anyone with tips to how to solve mole questions. those r very hard or me. n anyone have any idea as what can be asked. thanks in advance

Do u have any specific question?..ask it and im sure someone will help u :)
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: dodo on May 19, 2010, 12:03:09 pm: hey does any one know when is chemistry parictcal paper for ASLevel
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: master786 on May 19, 2010, 12:05:08 pm: tomororw
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: LLawliet81 on May 19, 2010, 01:30:29 pm: I think it will be identification, thermochemistry and find molarity.

Anyone knows about identification of Cobalt ? Need help :)
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: poisonedrose on May 19, 2010, 02:17:14 pm: I have a feeling there will be identification of ions, enthalpy change and water of crystallization.
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: LLawliet81 on May 19, 2010, 02:28:54 pm: What is the example of crystallization experiment ?
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: winnie101 on May 19, 2010, 03:03:14 pm: anyone who has done mj 09 paper 31, could u plz explain the mole questions in part c. i just get how to do the first 2 moles questions
Thanks
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: Phosu on May 19, 2010, 04:08:59 pm: i) for first step they have given u the concentration, ur titre value is the vol of Na₂S₂O₃
so to find moles apply n=cv, n= .15 x titre/1000

ii) next is simple mole ratio which can be found from the equations
S₂O₃^2- : I₂
2 : 1
i) : x

iii) again its the same as above
Cu²⁺ : I₂
2 : 1
x : ii)

iv) now we know the moles present in Cu²⁺ and we have the volume (25cm³ dissolved in FA3)

iii) = c x 25/1000

v) im not really sure bout this one
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: ruby92 on May 19, 2010, 04:19:50 pm: M/j 2009 variant 32
c step 3 4 5???
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: aldehyde1612 on May 19, 2010, 04:22:02 pm: im not sure but i think the last step involves C₁*V₁ = C₂*V₂

so.. concentration of FA2 = concentration of FA3*Volume (250 or something) divided by Volume of FA2 buretted (the amount at the beginning when making FA3)

if that makes sense. :-\
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: superduper2009 on May 19, 2010, 05:35:07 pm: how do find water of crystallization???
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: XaM!! on May 19, 2010, 06:13:47 pm: For water of crystallisation just follow the instructions... basicaly a test tube and a salt is given. a specific mass is asked. first u have to find mas of empty test tube. thn add salt and measure mass(mass is gven in ques whch u have to take).
now heat the test tube at medium flame. do it for 5-8 mins to ensure water is eliminatd. nw cool the tube n measure mas. again heat the test tube for another 5mins n cool n measure, thn compare if masses r the same as the recent one thn all the water is eliminated... if the mas is change thn again heat n measure mass. when it becomes constant. nw use this mass for further calculations to calculate X in salt.X.H2O... that x is water of crystallisation...
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: joggingday on May 19, 2010, 06:15:45 pm: Quote from: ruby92 on May 19, 2010, 04:19:50 pm
M/j 2009 variant 32
c step 3 4 5???

Step 3:
To calculate moles of ethanedioate ions that reacted with the KMnO4 : Use the mol ratio from 2nd step. You find that for every 2 mol of MnO4- ions, there are 5 moles of ethanedioate ions. So :

Answer = (Mol of KMnO4/2) * 5

Step 4: You know the volume of FB3 used in the titration was 25 cm3. So molarity = mol of ethanedioate ions/volume in dm3
Volume in dm3 will be 25/1000= 0.025

Step 5: You now have the concentration in mol dm-3 from step 4. This tells you that there are x mol in 1000cm3. You have to multiply this value by 1000 to get the "total" moles. Then divide this answer by the volume of FB2 used (which should be between 42.5 and 43.0 cm3)

Step 6: From step 5 you have the number of moles per dm3. To find the amount of grams per dm3, simply multiply your answer in step 5 by the Mr, to get the mass per dm3. In this case it will be:
concentration * 126

Hope this helps
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: Ro1024 on May 19, 2010, 06:21:00 pm: hey, could anyone who does the exam earlier post some of the questions that come up?
cos i am reallly crap at practicals! let me know, i do it on thursday! PAPER 31...
Anyone??
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: ruby92 on May 19, 2010, 06:55:28 pm: Quote from: joggingday on May 19, 2010, 06:15:45 pm

Step 3:
To calculate moles of ethanedioate ions that reacted with the KMnO4 : Use the mol ratio from 2nd step. You find that for every 2 mol of MnO4- ions, there are 5 moles of ethanedioate ions. So :

Answer = (Mol of KMnO4/2) * 5

Step 4: You know the volume of FB3 used in the titration was 25 cm3. So molarity = mol of ethanedioate ions/volume in dm3
Volume in dm3 will be 25/1000= 0.025

Step 5: You now have the concentration in mol dm-3 from step 4. This tells you that there are x mol in 1000cm3. You have to multiply this value by 1000 to get the "total" moles. Then divide this answer by the volume of FB2 used (which should be between 42.5 and 43.0 cm3)

Step 6: From step 5 you have the number of moles per dm3. To find the amount of grams per dm3, simply multiply your answer in step 5 by the Mr, to get the mass per dm3. In this case it will be:
concentration * 126

Hope this helps

thanks a lot :)
just one question in step 5 we multiply the conc found in step 4 with 1000?
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: Ro1024 on May 19, 2010, 08:53:58 pm: are there titrations in paper 31?????
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: AS-Girl on May 19, 2010, 09:31:21 pm: Quote from: Ro1024 on May 19, 2010, 08:53:58 pm
are there titrations in paper 31?????

God only knows..

Reminder: No discussion of exams or predictions!!
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: MistahNobodeh on May 19, 2010, 11:36:10 pm: Quote from: Ro1024 on May 19, 2010, 08:53:58 pm
are there titrations in paper 31?????
Actually that depends paper by paper. We could get anything at all. Anyways I will really hope that we get Enthalpy cuz I practiced really hard on those.
Can u believe it?? Our teacher didn't practice with us ONE enthalpy question the whole year. Not ONE. And in Mocks she gives an enthalpy question.
Anyways that had me convinced that we may get enthalpy instead of Titration this year. Also can anyone confirm if v r going to get 3 practicals in a paper now rather than the usual 2?? Well May June 09 had 3 but October November had 2 so...I am confused. Is there a trend??
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: Ro1024 on May 19, 2010, 11:58:14 pm: i think, they might give is an enthalpy change prac as well as an analysis and a organic one as well!
3 pracs in total.. i think, cos most of the time goes in the titration and if a titration is not there, then the time might be equal for all 3 instead of 2.
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: superduper2009 on May 20, 2010, 12:21:21 am: what stuff do we need to know in organic chemistry?
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: Ro1024 on May 20, 2010, 12:55:40 am: anyone malysian?? xD please reply to this thread or send me an inbox! need to talk urgently!
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: superduper2009 on May 20, 2010, 01:33:45 am: how do u differentiate between aluminum and lead ions???
how do u differentiate between ketones and aldehydes???
how do u differentiate between the halogens???
how do u differentiate between sulfates and sulfites???
How do u test for carboxylic acids...
how do u test for alkanes and alkenes?
thanks in advance :D
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: Candela on May 20, 2010, 01:42:58 am: sulfate & sulfite is given in the analysis notes.
sulfate- gives white ppt with Ba²⁺ or Pb²⁺ (insoluble in excess dilute strong acid)

sulfite- gives white ppt with Ba²⁺ (soluble in excess dilute strong acid)
So₂ liberated with dilute acids!
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: ifraha18 on May 20, 2010, 02:04:43 am: can nione tel me some past pprs in whch enthalpy was given..??plz...
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: forkasha on May 20, 2010, 02:25:43 am: i think nov09
Title: Re: CHEMISTRY. P3. CIE.. advice and titrations?
Post by: piggydiggy on May 20, 2010, 12:16:08 pm: i hate my question no 1 on paper 32.. arghh ! that was like crazy, i studied about titration and there's no titration at all. great.