This discussion is now closed.

Check out other Related discussions

Chemistry Exams 19/06/06

Good Luck Everyone!!! hope it all goes well.. and i thought people could post here after they've finished, and tell us all how it went... (nothing like a good old exam postmortem. :biggrin:

)

Reply 1

SFC_FOREVER!

1

It went brilliant, although thats probably because it hasn't started yet. Have OCR Salters in an hour and a half. Cant wait.

Reply 2

gfdsa

edexcel chem 5 went pretty well for me.

Reply 3

Dal

2

i agree... unit 5 wasnt bad.. but i didnt like the rate question where they asked you to suggest a mechanism for A+B->AB3! i made up nonsense!
unit 4 was ok i think..althouhg i feel like i did better on unit 5..

Reply 4

GarageMc

1

Jesus christ food science was stupendous

Reply 5

SFC_FOREVER!

1

Salters was ****, as per usual. Why o why do they always concentrate on one area of the exam. Isn't it meant to be testing my knowledge on all units which may come up in the paper? ******s

Reply 6

Clearvision

Unit 5 was OK, but had some tricky parts to it.

I thought the 24, DNPH question was evil. As was the question about A,B and the rate determining step, anyone got an answer for the AB one?

My calculation answers were...

k = 2 mol^-2 dm^6 s^-1
Ea = 107511k
37.3% Iron (II)
E cell = +1.59v

Comments?

Reply 7

ArVi

13

Dal

i agree... unit 5 wasnt bad.. but i didnt like the rate question where they asked you to suggest a mechanism for A+B->AB3! i made up nonsense!
unit 4 was ok i think..althouhg i feel like i did better on unit 5..

Reply 8

tazzalc

I got 74.5% on the iron question
106 200 kJ mol^-1 for the activation energy

I thought it was quite a tricky paper though...how did everyone else feel bout it?

Reply 9

ArVi

13

Clearvision

37.3% Iron (II)

Comments?

I got 74.5% :confused:

All other answers are the same

Reply 10

uk6458

on salters chemistry by materials, what did people get for the calculation question, for the H2O2 concentration?? :smile:

Reply 11

Clearvision

hmm how did i get 35.3%

8.04x10^-4 mol of Fe(II) ions...

6/278 mol of the tablets...

moles of Fe(II)/moles of tablets *100 = 35.3 ??? Must be wrong if two people have 74%..how did you get 74%?
---
And was your gradient something like 5625?

I obviously messed up my units for the Ea :-/

---

For the AB rate determining step question what did you put?

I put SN1 and put that the rate determining step depended on the conc of B. But that doesn't sound good to me, as the orders were 1 and 2(?) and SN1 involves 1 and 0. But it couldn't be sN2 as that doens't havea rate determining step and i couldn't think of any other relevant mechanisms.

Reply 12

ArVi

13

tazzalc

I got 74.5% on the iron question
106 200 kJ mol^-1 for the activation energy

I thought it was quite a tricky paper though...how did everyone else feel bout it?

I got 110kJ mol^-1

74.5% on the Fe question :smile:

Reply 13

SFC_FOREVER!

1

uk6458

on salters chemistry by materials, what did people get for the calculation question, for the H2O2 concentration?? :smile:

The one about undiluted etc.. I got 0.09mols. Dont ask me how I got there :biggrin:

Reply 14

tazzalc

Clearvision

hmm how did i get 35.3%

8.04x10^-4 mol of Fe(II) ions...

6/278 mol of the tablets...

moles of Fe(II)/moles of tablets *100 = 35.3 ??? Must eb wrong if two people have 74%..how did you get 74%?
---
And was your gradient something like 5625?

I obviously messed up my units for the Ea :-/

Yeah my gradient was -5555 or something like that which is pretty similar.

Reply 15

Clearvision

Haha sorry, my gradient was negative.

Urgh explanation of the Iron question is needed :frown:

Can't believe i messed up a calculation...

What did you put for the question about C=O and C=C and their respective mechanisms?

I think i got two marks talking about C=O being susceptible to nucleophilic attack and C=C electrophilic attack.

How many people know that 2,4,6 tribromophenol was a white ppt and the structure of the reacted form of 2,4DNPH?

I can't believe they put 2,4DNPH in unit 5 as it was in unit 4 for the first time in january.

Reply 16

tazzalc

Clearvision

Haha sorry, my gradient was negative.

Urgh explanation of the Iron question is needed :frown:

Can't believe i messed up a calculation...

What did you put for the question about C=O and C=C and their respective mechanisms?

I think i got two marks talking about C=O being susceptible to nucleophilic attack and C=C electrophilic attack.

How many people know that 2,4,6 tribromophenol was a white ppt and the structure of the reacted form of 2,4DNPH?

I can't believe they put 2,4DNPH in unit 5 as it was in unit 4 for the first time in january.

Sorry can't help u with explanation of iron question. I can't remeber a thing, only the answer.

I also said that about the C=O and C=C. I said that C=C had a high electron density so was attacked by electrophiles. I also said that in the C=O bond, the O was polarising and made the C delta +ve which was therefore susceptible to attacks by nucleophiles.

I knew about the white ppt but sisn't know the structure for the 2,4-DNP.

I completely screwed up the one about NMR spectrum and their areas under the peaks!!!

Reply 17

=Keith=

3

Both papers were ok but im almost killing myself now. I got the % answer as 74.something i thought that my answer was wrong. I cut the method and did somehting crap and got 9% ... lost 5 marks which i could gain easily !!!!! argh !!!!
Unit 4 sounded easy to me, unit 5 was good but compared to pastpapers it was tricky, dont u guys think? Unit 5 pastpapers are much easy

Does anyone know the grade boundaries for unit 4 and 5?
Ne ways biology tmrw and i have no time to prepare for it :frown:

Reply 18

Clearvision

Hmm it was... 20.1cm^3 0.02moldm^-3 KMnO4 was needed to complete 20cm^3 of 6g of tablet made into 200/250cm^3 of solution.

The equation was a 1:5 ratio of KMnO4-Fe(II)?

Anyone care to have a go...

I actually think my answer was 37.2...rounded up to 37.3 so it could be i had half the actual answer, or something.

I thought it was tricky compared to PP's, but there was still alot of similair stuff in it, just a few different bits...that i struggled with :tongue: