AQA CHEM4 discussion/unofficial mark scheme

Reply 20

Eriano303

1

I actually thought I was going to do well in this paper but no :angry:

screw you AQA

Reply 21

mgill17

6

Yeah they will have been step 3 and 4 i just couldn't remember the numbering in the question

Reply 22

DDan123

8

Could you not write KCN dissolved in ethanol?

Posted from TSR Mobile

Reply 23

iselhong

1

Original post by mgill17

So I think this was Question 8

It asked how to basically get an alcohol from an ester
I basically described Base Hydrolysis...so using NaOH and heating under reflux. Then distilling it off.
I guess you could've described Acid Hydrolysis too and there's another one some people at my college put but I can't remember that one.

The structure of S was the same bromoalkane it gave you (was it 2-bromobutane? I can't remember) but you swapped the Br for a Nitrile group

Step 1
Reagent was KCN
Conditions was aqueous

Step 2
Reagent was LiAlH4
Conditions was dissolved in ether

---I think that was it someone correct me if I'm wrong------

it should be ethanol and water mixture to convert haloalkane to nitrile isn`t it?

Reply 24

sean.17

1

Original post by DDan123

Could you not write KCN dissolved in ethanol?

Posted from TSR Mobile

I said KCN in ethanolic conditions, I think they may accept that

Reply 25

Anon_98

19

Nah, that NMR one lmao. I knew NMR would haunt me, but that was just... ugh.

I'm so sad that I'm not sad. - I don't even have time to mourn bc maths tomorrow which I cba for now. ):

Well, I guess we still have unit 5.

Reply 26

mgill17

6

Original post by iselhong

it should be ethanol and water mixture to convert haloalkane to nitrile isn`t it?

Oops yeah. I meant ethanolic that's what I put in the paper. Idk why I put aqueous there..I'll change it!

Reply 27

username1539513

21

Original post by Anon_98

Nah, that NMR one lmao. I knew NMR would haunt me, but that was just... ugh.

I'm so sad that I'm not sad. - I don't even have time to mourn bc maths tomorrow which I cba for now. ):

Well, I guess we still have unit 5.

The entire paper was horrible and ugh imho

Best of luck with your maths, I hope it isn't as bad as this paper was.

You still have Unit 5, I already did it and got a B in it, Unit 5 is easier

Reply 28

AnnaL2243

1

Such a horrible paper!!! The questions were so difficult and it was far too long! I ran out of time 😥

Reply 29

Econ/Chem/FMaths

10

Reaction orders : A-1
B-2

Reply 30

DDan123

8

Just so gutted. Not sure if I got an A and the Empa wasn't great either. Think I need like full UMS unit 5 lool

Posted from TSR Mobile

Reply 31

shellypatel2

1

Original post by logicmaryam

Heey guys, I think we can all agree this paper was one of the hardest CHEM4 papers ever.
We'll discuss the answers and compile an unofficial mark scheme. Post your answers here!

Q1 20 marks
a) Ethanoic acid in water
CH3COOH ⇌ CH3COO- + H+ (1)
b) Ethanoic acid as base with HNO3
HNO3 + CH3COOH = CH3CHOOH2+ + NO3- (1)
c) pH of acid? 2.08 (3)
d) pH when alkali added to acid 2.32 (4)
e) [salt]/[acid] = 3.33 (3)

why is chloroethanoic acid stronger than ethanoic acid? (2)
Chlorine is more electronegative so will withdraw electrons and weaken the O-H bond so H is lost more easily

I got CH3COOH + H2O ⇌ CH3COO- + H3O+ bc it said reaction with water?

Reply 32

Anon_98

19

I agree.

Thank you + I don't think it'll be, no. Or at least I v much hope not bc it's one of the 'easy' resits.

Oh, nice, I see! Yeah, I also find unit 5 a whole lot better. :'3 Good luck with your next exam too.

Reply 33

RedNebula

14

Original post by shellypatel2

I got CH3COOH + H2O ⇌ CH3COO- + H3O+ bc it said reaction with water?

I put this too, I'm not sure though :smile:

Posted from TSR Mobile

Reply 34

RedNebula

14

Original post by iselhong

Did anyone work out the last question ? i ran out time to finish the explain bit.
i did something like (HO)CH2CH2C(CH3)2CH2(OH)

I think it's CH3 O C(CH3)2 CH2CH2 OH
Anybody else get this?...

Posted from TSR Mobile

Reply 35

Azzer11

17

Original post by MuslamicJihad

The nmr at the end was (I think): CH3OCH2CH2C(CH3)2OH

This was what I got and it was the most common mistake on the last question. That is a tertiary alcohol and the question clearly said that the compound could be reduced by potassium dichromate which means that it cannot have been a tertiary alcohol.

Reply 36

HBrookes

1

That was officially the worst paper ever and Aqa were very harsh, why did they have to change the syllabus on our year and therefore because we're the final year sitting it they decided to make it memorable. Here's to hopping the grade boundaries are rock bottom. :redface:

Reply 37

QWERTYYTREWQ17

4

Original post by RedNebula

I think it's CH3 O C(CH3)2 CH2CH2 OH
Anybody else get this?...

Posted from TSR Mobile

Yessss mate same here

Reply 38

JK11

8

what did everyone get for Q3f? it was about lidocaine hydrochloride

Reply 39

neevtrehan

1

Original post by logicmaryam

Heey guys, I think we can all agree this paper was one of the hardest CHEM4 papers ever.
We'll discuss the answers and compile an unofficial mark scheme. Post your answers here!

Q1 20 marks
a) Ethanoic acid in water
CH3COOH ⇌ CH3COO- + H+ (1)
b) Ethanoic acid as base with HNO3
HNO3 + CH3COOH = CH3CHOOH2+ + NO3- (1)
c) pH of acid? 2.08 (3)
d) pH when alkali added to acid 2.32 (4)
e) [salt]/[acid] = 3.33 (3)

why is chloroethanoic acid stronger than ethanoic acid? (2)
Chlorine is more electronegative so will withdraw electrons and weaken the O-H bond so H is lost more easily

I swear e is wrong, I got 1.2 instead of 3.33

AQA CHEM4 discussion/unofficial mark scheme

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you