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AQA CHEM4 discussion/unofficial mark scheme

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How many marks was the question to distinguish between two optical Isomers? I don't remember doing it, think I might have not seen it by accident :frown:


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Original post by mgill17
It was synoptic and incredibly sneaky of aqa. They're the worst:frown:


Yes it was unfortunately. A disgusting paper😭
Original post by logicmaryam
oops typo! will change it now


(Or just 'chloroethanoyl chloride' as the only place another chloro group could be is carbon 2).

Thanks for producing an unofficial mark scheme by the way, I really appreciate it!
Original post by mgill17
Oh was that the one that wanted you to prove the molecular formula for the compound was C6H14O2?
It was 3 marks.
It gave you the percentages of Carbon and Hydrogen (so you could work out Oxygen) and then gave you an m/z ratio.
Totally messed that one up. Couldn't do it. Did anyone manage to do it?


Ill update it with my working for you!
Want to die after that
Original post by mgill17
I'm guessing I've got 2 of the marks then. I don't know whether it's a bad thing or a good thing I didn't have to resit unit one because I would've actually have revised empirical formula then, I tried to work out an empirical formula with minimal confidence in what I was doing, then I think I did the last step the wrong way around...thanks aqa


lol yeah I had to resit chem 1 as I got a B last year but kinda glad I did now or I probs wouldn't have got that question. Times like this make you realise how unfair life is, I'm pretty sure chem 4 is NOT meant to be synoptic??? What's the point in modules omg
Original post by isaisababy
There was only 1 place the chlorine could be so the number isnt needed, but I think 1- is wrong whereas 2- would be in brackets in the MS


agreed. dont know how it can be 1-choloro. i put 2
Original post by DDan123
How many marks was the question to distinguish between two optical Isomers? I don't remember doing it, think I might have not seen it by accident :frown:


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if you get an answer to this can you hit me quote me please because i clearly too skipped over that

i just remember them asking us what a racemic is
Original post by Cadherin
Sorry!

So, reagent is NaOH and for a base hydrolysis like that, you need to reflux it (so high temperature).


Don't worry it's fine haha,in my textbook it does say reflux but it also says dilute NaOH which I why I was wondering if you can have both?
Original post by hi-zen-berg
if you get an answer to this can you hit me quote me please because i clearly too skipped over that

i just remember them asking us what a racemic is


That question wasnt there so dont worry.
Original post by Cadherin
Sorry!

So, reagent is NaOH and for a base hydrolysis like that, you need to reflux it (so high temperature).


Don't worry it's fine haha,in my textbook it does say reflux but it also says dilute NaOH which I why I was wondering if you can have both?
Original post by logicmaryam
That question wasnt there so dont worry.


Phew! Also was writing they are optical isomers for the previous question not enough? Or did you have to specify they are mirror images of each other?


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Original post by Lolaturface
lol yeah I had to resit chem 1 as I got a B last year but kinda glad I did now or I probs wouldn't have got that question. Times like this make you realise how unfair life is, I'm pretty sure chem 4 is NOT meant to be synoptic??? What's the point in modules omg


I agree, if it is a CHEM4 paper you should be tested in CHEM4 content. Nothing synoptic worth that many marks and don't even get me started on some of the questions that were CHEM4 based but just utterly ridiculous.

This poor excuse of a paper has literally cost me my grade for university and I'll be literally heartbroken if this paper is the reason I don't get in. I literally got 85 and above in all the other past papers for this unit but I think I've got about 67/68 in this. And my CHEM5 will probably not be enough. I understand that obviously the content has to get harder over the spec lifetime but this was a whole new level.
Original post by DDan123
How many marks was the question to distinguish between two optical Isomers? I don't remember doing it, think I might have not seen it by accident :frown:

I haven't seen it either, I remember thinking if they asked me id have no problem answering! so confused
Rate equation when propanone or something is increased
rate = [H+]
because propanone is in excess, H+ is limiting factor.


i said the rate =k[propanone] coz Rate = k[H+][propanone] ,when propanone is large , H+ has small effect on the rate ...
i think i am wrong then
Some teacher put his grade boundary predictions for this paper on twitter:

A* - 83
A - 76
B - 69
C - 62
D - 55
E - 48
How many marks for the rate equation question(rate =[H+])? 2?
In question 1:

First question 1 mark, second question 1 mark, third question 2 marks
The salt was sodium ethanoate (1)
Why is chloroethanoic acid stronger than ethanoic acid was 2 marks
Answer: Cl withdraws electron density, so O-H bond weaker OR reduces negative charge on COO- OR COO- more stable (from a previous markscheme)
Original post by iselhong
Rate equation when propanone or something is increased
rate = [H+]
because propanone is in excess, H+ is limiting factor.




i said the rate =k[propanone] coz Rate = k[H+][propanone] ,when propanone is large , H+ has small effect on the rate ...
i think i am wrong then



That's what I put, but then again I'm not a chem wizard
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Anerror
Original post by mgill17
Yep. It was after something with the molecular formula C6H14O2


Okay good. Only thing I thought I got right aha.

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