Equilibria, Energetics and Elements (F325) - June 2011 Exam.

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Yes, I believe it just asked for the ratio of the concentrations needed.

You also had to write equations for the preparation of the buffer.

CH_3COHCOOH + NaOH -> CH_3COHCOO^{-}Na^{+} + H_2O[br][br]

It's important to say it's only partially neutralised, with an excess of the acid.

Did it say that? I remember seeing deduce the chemicals, proportions then magic tang.

Reply 2541

yu80359

there is not point to discuss without a copy of Question paper
so please who ever got the paper upload it asap
I am begging you

Reply 2542

CoventryCity

On the whole the hardest Q was the buffer/magic tang one imo, other tricky bits were to deduce the repeating unit in the 4,4 bipy complex ion, the KOH on the electrode potentials and some of the ionic equations on 8). All the other bits were ok imo

Reply 2543

jam.wa

Original post by Intollerant

Anyone know the answer for the % of copper in the alloy?

Well I got 67.6%, but some people got blahdeblahdeblah.

Reply 2544

RealisticDeity

"I am writing to complain about the contents of todays chemistry paper. It is my opinion that the difficulty of paper was constantly high, with a couple relatively easy questions scattered throughout; the paper does not offer a wide representation of various skills and abilities; it merely appears to be separating the A* students from the main group."

Copy and paste this to [email protected]; if enough people send it, we may get some sort of investigation into why OCR are inherently complete ****tards!

Reply 2545

jontylol

Probably lost about 30 marks im guessing :/

Reply 2546

Soloman

I love all the stress

Reply 2547

CoventryCity

Original post by BA1

Yes, I believe it just asked for the ratio of the concentrations needed.

You also had to write equations for the preparation of the buffer.

CH_3COHCOOH + NaOH -> CH_3COHCOO^{-}Na^{+} + H_2O[br][br]

It's important to say it's only partially neutralised, with an excess of the acid.

Yes I did this bit about neutralisation with excess acid, I calculated [H+] and Ka correctly.
Maybe could have got a few marks

Reply 2548

Lucy23

Original post by Intollerant

Anyone know the answer for the % of copper in the alloy?

I got 67.6 %

Reply 2549

jam.wa

Original post by Soloman

I love all the stress

HahahAHHAA111!!

Reply 2550

InsaneFandom

First biology, then chemistry...not looking forward to physics :|

Reply 2551

Lucy23

Original post by LilacTweet

Could anyone go through the hydration one? I got confused when there was another arrow under the lattice enthalpy.....

The ions are hydrated separately so there are two different values for enthalpy of hydration

Reply 2552

786girl

i have lost ATLEAST 37 marks.... :frown:

theres prolly more that i am not aware of
ahhhh

Reply 2553

lmfw

I've lost will to revise. I've got four exams left and they are ALL OCR. Anyone else feel this way? :/

Reply 2554

LilacTweet

Original post by Lucy23

The ions are hydrated separately so there are two different values for enthalpy of hydration

Can you remember the whole question enough to go through it please? (:

Reply 2555

mitch1234

i don't think the actual questions in the paper were that bad. it was more of a time issue. usually at the pace i was going at i would have at least had 15 minutes to check over answers but had like 1 minute if that. some of the questions were a bit ambiguous like the magic tang one and the last question was hard, but the last question usually is about that hard on chemistry papers. i just think they tried to put too much in for the time limit. if it was a bit shorter people would have had time to think about the questions and not make stupid mistakes which i know i made plenty

Reply 2556

pan_93

Original post by touran22

im uploading some of the questions now..

http://imageshack.us/photo/my-images/593/photoozf.jpg/

hi mate...are you going to upload it? everyone's itching to see it:P

Reply 2557

blush.ox

Didnt answer about 18 and according to this thread i've lost a further 15. I probably made a few errors here and there aswell.

Who thinks 60/100 for an A would be reasonable?

Reply 2558

jam.wa

Does anybody know how to make dangerously acidic sweets? Only, I was thinking we should thank OCR, thank them for that paper, give them some sweets. Donate some protons into their stupid faces.

Reply 2559

terry_2006

Original post by cawse879

I did benzene for the buffers one said add in sodium benzanoate to generate the conjugate base c6h5c00-. and then worked out the ratio to be 0.23 using. [H+]= Ka * [C6H5COO] / [C6H5COONa] ? maybe 3 or 4 marks perhaps?

omg i have chosen that one as well=.= i have the same answer as you had but i am not sure if the choice was correct as i have rushed it. However i hope i can get at least 3-4 marks for showing the work out nicely.