AQA CHEM4 discussion/unofficial mark scheme
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Original post by RME11
For last question I just put all of the structures that would be present due to the spectra, that it would be a primary/secondary alcohol and from the IR spec only no C=O/C=C bonds, then the displayed structure which was CH3OCH2CH2C(CH3)2(OH) - I really don't know what else you could have said/done for that.
Wouldn't that be a tertiary alcohol?
I made far too many stupid mistakes and missed out far too many questions. Probably got a low C so unless I've done well on CHEM1 resit and can get full UMS in CHEM5 then I haven't got an A and it's goodbye UCL.
Original post by RME11
For last question I just put all of the structures that would be present due to the spectra, that it would be a primary/secondary alcohol and from the IR spec only no C=O/C=C bonds, then the displayed structure which was CH3OCH2CH2C(CH3)2(OH) - I really don't know what else you could have said/done for that.
Swap the C(CH3)2 with one of the CH2 groups and it would've worked. Hopefully only 1 mark lost for the tertiary alcohol.
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Original post by Azzer11
Swap the C(CH3)2 with one of the CH2 groups and it would've worked. Hopefully only 1 mark lost for the tertiary alcohol.
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Posted from TSR Mobile
Thankyou!
I was wondering, you know it said explain your answer? Does drawing stuctures for the different components count as explaining e.g I said 2.1 - Then drew the structure ?
Does anyone have predictions of grade boundaries? People are saying A* = 83/82?
Also how many marks do you think I'd get for question 9 for:
Identifying O-H bond from IR spectrum
Identifying -OH from NMR spectrum (from it's ppm value, 1 H atom in its environment)
Identifying R-O-CH2 (from it's ppm value, 2 H atom in its environment)
Identifying C(CH3)2 (from it's ppm value, 6 H atom in its environment)
Thanks!
Also how many marks do you think I'd get for question 9 for:
Identifying O-H bond from IR spectrum
Identifying -OH from NMR spectrum (from it's ppm value, 1 H atom in its environment)
Identifying R-O-CH2 (from it's ppm value, 2 H atom in its environment)
Identifying C(CH3)2 (from it's ppm value, 6 H atom in its environment)
Thanks!
Original post by EKA Mathsboy
*1 hour before exam
yep im ready AQA! come at me!
*1 hour after exam
Well, id better switch my application to maths
yep im ready AQA! come at me!
*1 hour after exam
Well, id better switch my application to maths
If you're on AQA maths, bet you've changed your mind on that front
Original post by Azzer11
Swap the C(CH3)2 with one of the CH2 groups and it would've worked. Hopefully only 1 mark lost for the tertiary alcohol.
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I initially put that but the O-CH2-R group was a triplet, it needed 2 protons in the adjacent carbon.
Original post by A sheesh
Ahh chem4, I feel for you guys, so glad I'm done with a levels 😁
If anyone is unsure of an answer to a question I can try help?
Currently doing a chem degree at UoM
If anyone is unsure of an answer to a question I can try help?
Currently doing a chem degree at UoM
This is actually a chem5 question
On the AQA complex ions sheet, the reaction of copper(II) with NaOH is listed as a substitution reaction. This has confused me because I thought the water ligand wasn't substituted but instead donated a proton to the hydroxide ion, acting as a bronsted-lowry acid :/
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Hey- for the question with the zig zag thing asking for the section of the polymer , I drew a dipeptide on the zig zag they gave (and labelled it as a dipeptide) then drew the correct reporting unit (again labelled) underneath but I forgot to cross out... Do you think i would still get the marks?
Also for the question on te most abundant cl... Does anyone know if the anwser was 112 or 114?
And the question about base hydrolysis - did you have to say dilute naoh? And instead of reflux could you have used a condensation Colum/ filtration?
Finally (sorry for all the qs) xD
For the poylester vs polyalkene q could u have said biodegradable or do you have to relate it to medicine ? I talked about hydrolysis and stuff but just forgot to relate it back
Thank you !!
Also for the question on te most abundant cl... Does anyone know if the anwser was 112 or 114?
And the question about base hydrolysis - did you have to say dilute naoh? And instead of reflux could you have used a condensation Colum/ filtration?
Finally (sorry for all the qs) xD
For the poylester vs polyalkene q could u have said biodegradable or do you have to relate it to medicine ? I talked about hydrolysis and stuff but just forgot to relate it back
Thank you !!
Original post by Fibsy
On the AQA complex ions sheet, the reaction of copper(II) with NaOH is listed as a substitution reaction. This has confused me because I thought the water ligand wasn't substituted but instead donated a proton to the hydroxide ion, acting as a bronsted-lowry acid
think i get what you mean. It makes sense that you think it's not substituted correct me if I'm wrong but the equation I believe isCu(h20)6 2+ + 2oh- -----> cu(h20)4(oh)2 + 2h20the complex is effectively a Lewis acid as its losing protons. The OH- is effectively acting as a base (formation of water)So it could be seen as the complex losing two protons to the OH- which is then essentially not a substitution which is correct but I think they've labelled it as substitution for simplicity for alevels as technically, it's the same as substitution in terms of replacing ligands
Think I might be having to say goodbye to UCL as well 😢
Did anyone else get zero order for X?lol
I am always loathe to look at and contribute to these "unofficial answer" threads but due to the furore about the NMR question I felt the need to have a look myself and I REALLY don't see what all the fuss was about. It was a 9 mark question where you can get the majority of the marks just for looking at the IR and NMR and writing what you know. I do agree the final structure was a little tricky, especially the need for it to be a tertiary alcohol. Below is my working out for this question, be aware I am NOT an examiner, and do NOT have access to the correct answers, but this seems correct to me.
For all those worrying about what you got in this exam, my advice to you is concentrate on the next one as there is NOTHING you can do about this one other than worry.
Best of luck either way!
Alex
For all those worrying about what you got in this exam, my advice to you is concentrate on the next one as there is NOTHING you can do about this one other than worry.
Best of luck either way!
Alex
Original post by RedNebula
Yes, same! Not sure what all the tertiary alcohol business was about
Original post by emilies18
Hey- for the question with the zig zag thing asking for the section of the polymer , I drew a dipeptide on the zig zag they gave (and labelled it as a dipeptide) then drew the correct reporting unit (again labelled) underneath but I forgot to cross out... Do you think i would still get the marks?
Also for the question on te most abundant cl... Does anyone know if the anwser was 112 or 114?
And the question about base hydrolysis - did you have to say dilute naoh? And instead of reflux could you have used a condensation Colum/ filtration?
Finally (sorry for all the qs) xD
For the poylester vs polyalkene q could u have said biodegradable or do you have to relate it to medicine ? I talked about hydrolysis and stuff but just forgot to relate it back
Thank you !!
Also for the question on te most abundant cl... Does anyone know if the anwser was 112 or 114?
And the question about base hydrolysis - did you have to say dilute naoh? And instead of reflux could you have used a condensation Colum/ filtration?
Finally (sorry for all the qs) xD
For the poylester vs polyalkene q could u have said biodegradable or do you have to relate it to medicine ? I talked about hydrolysis and stuff but just forgot to relate it back
Thank you !!
1. I don't know - their general principle is right + wrong = wrong
2. It should be 112.0 but in a past paper which asked the same but with a different compound they allowed two answers (hence 114.0)
3. I don't know - but on all of my revision sheets dilute is a must, I'm pretty sure they would only allow heat under reflux
4. I don't know - but I and many others mentioned biodegradable, normally in markschemes they just want the science so you should be fine
(edited 7 years ago)
Original post by Fibsy
This is actually a chem5 question
On the AQA complex ions sheet, the reaction of copper(II) with NaOH is listed as a substitution reaction. This has confused me because I thought the water ligand wasn't substituted but instead donated a proton to the hydroxide ion, acting as a bronsted-lowry acid :/
Posted from TSR Mobile
On the AQA complex ions sheet, the reaction of copper(II) with NaOH is listed as a substitution reaction. This has confused me because I thought the water ligand wasn't substituted but instead donated a proton to the hydroxide ion, acting as a bronsted-lowry acid :/
Posted from TSR Mobile
I always thought of it as B-L reaction
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