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Aqa chem 4/ chem 5 june 2016 thread

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Original post by BeckaH2
Agreed, which is ridiculous seeing as the country desperately needs more people in these (and similar) professions!


They make it trickier every year to get the grades, unfortunately for us, we're the last year with this syllabus so most of the 'easy' questions have already been used. This year was ridiculous though, they pretty much made the whole paper 'different' excluding some questions..

Hardly any marks for any of AS chem / Chem4 tests/mechanisms etc.. I revised them so much and it sucks that there was like 5 marks on it..
hey guys, so it was definitely a worse paper than the past few years but do we have a estimation for grade boundaries? and would 70 realistically get a B? thanks and hope everyone does a bit better in chem 5 :smile:
Can someone put the topics of each of the 9 questions up please
has anyone made an unofficial markscheme yet
my thought exactly
Original post by Kay Fearn
They make it trickier every year to get the grades, unfortunately for us, we're the last year with this syllabus so most of the 'easy' questions have already been used. Hardly any marks for any of AS chem / Chem4 tests/mechanisms etc.. I revised them so much and it sucks that there was like 5 marks on it..


I thought they'd reuse more questions but maybe change the numbers considering it's the last one of the spec, but no! For the mechanism question that only wanted the first step, I wrote the whole damn thing!! Just didn't have time to think straight, gutted there wasn't more mechanisms as I'd say out of everything that's what I'm most confident with :frown:
thoughts*
Original post by Kaya22
WP_20160614_17_31_50_Pro[1].jpg

this is the structure for question 9

it was an awful sneaky question guys i know


I showed all my workings but I didn't get the ether group or final structure right😔 Do you think they'll have marks for showing each group separately?
Apparently what has happened is they have a lot of questions that are slightly obscure that they have not used on previous papers but since this is the last series they have been putting all their unused questions in. Same goes for CHEM1 (which was impossible) and CHEM2 such a pain
Original post by bat_man
i said reflect plain polarised light in opposite directions.


99% sure the answer was ' they are non super imposable mirror images of each other
Original post by Suits101
That's why I doubted my answer, however I've linked the markscheme with the answer below this quote:



Markscheme for reaction with ethanoic acid and nitric acid from a different exam board - only difference is that this is with propanoic acid, page 8 part (d):
http://www.ocr.org.uk/Images/61528-mark-scheme-unit-f325-equilibria-energetics-and-elements-june.pdf

It wasnt quite the same question though



the OCR question specified 2 products, the AQA one didn't - I think the answer I gave is likely to be accepted but the one above will be the first answer
Dude 15/20 marks dropped is like a. a* which world are you in?


Posted from TSR Mobile
Original post by Anno007
H is not an R group. The 3.1-3.9 is for an ether group.


R group can be hydrogen...image.png
why am I even on here when i have an F214 in a couple of days



but seriously, screw chemistry. I'm just done with these silly questions, was hoping for nice buffer questions and a load of mechanisms but I get a 9 marker on NMR and 1 markers that took an average of 3 mins each to do
(edited 7 years ago)
1st question Ph calc
2nd question nucleophilic addition ethane12 diol
3rd question Kc value 9.09x10-3 answer mol-1 dm6
4th question electrophilic substitution
5th amino acid hydrolyse medical stitches
6 unsure
7 rate iodine h+ graph tangent r=k(H+)
8 8 marks for Naoh kcn hz Ni
9 molecular formula proof using empirical formula and that 9 marker 12 marks here

wat was question 6
O
Original post by Anno007
H is not an R group. The 3.1-3.9 is for an ether group.


Plus what would the chemical shift of a CH2 next to an alcohol group be then?
CHEM5 is our only hope 😩


Posted from TSR Mobile
Attempting version 1 of the unoffical mark scheme, will keep quoting this for others to see, may even start a thread. Please contribute i will update frequently before i start studying for my bio exam day after tomorrow heh rip

Equation representing ethanoic acid as a base with nitric acid:
CH3COOH + HNO3 -> CH3CO+NO3- + H2O

Advantage of using the polyester suture rather than the polyalkene?
the ester bond in polyester can hydrolyse whereas polyalkene C-C, C-H bonds are too strong thus cannot. Therefore the former can dissolve naturally whereas the former would require manual removal.

Identify what reagents are needed to distinguish between the two chlorine molecules, incl. observation. (Acyl chloride vs haloalkane (?))
Reagent: water/AgNO3 (?)/named carbonate
Observation: HCl fumes/White ppt./Effervescence -for the acyl chloride.

Which Nitrogen acts as a stronger base a vs. b (where a is attached to the benzene, and b is a tertiary amine) and why?
Nitrogen b due to the positive inductive effect of the carbons on the nitrogen, therefore making the lone pairs more available. Consequently nitrogen a is joined to a benzene so the lone pair delocalises into the benzene ring.

Order of reactions:
D 1 or 0 ??E 2

Why is the initial rate of the reaction used to determine the order of the reactants rather than at any other point during the reaction? Or something
Initial rate takes into account the initial concentration of the reactants which is more accurate since, as the reaction proceeds the concentrations of the different species change. (?)

How do you calculate the initial rate of the reaction from a graph of concentration against time?
Calculate the gradient of the tangent to the slope. (?)

Organic synthesis to produce the branched primary amine:
Structure: Same as previous however Br is substituted with CN
Step 3: KCN w/ ethanol (?)
Step 4: H2/Ni, LiAlH4

What is a racemic mixture?
Mixture containing equal quantities of each enantiomer.

How to distinguish between the two:
Expose to plane polarised light, rotates in opposite directions

Chiral Carbon relationship:
They are both mirror images of each other/enantiomers.

Question 9 Notes (I don't even need to say the question, everyone knows this question by the number... eek)
Potassium dichromate turns green, either a primary or secondary alcohol, or aldehyde
O-H absorption in the Mass spec
O-H in NMR spectrum, singlet obvs
CH3-O present in NMR spectrum, singlet
RCH2 in NMR spectrum, triplet ?
R(CH3)2 in NMR spectrum, doublet ? uh pls halp don't remember values.
Original post by Rob1245
hey guys, so it was definitely a worse paper than the past few years but do we have a estimation for grade boundaries? and would 70 realistically get a B? thanks and hope everyone does a bit better in chem 5 :smile:


I think it could be possible for 70 to be a B, as it was a hard paper and last year was 71
Original post by FireBLue97
1st question Ph calc
2nd question nucleophilic addition ethane12 diol
3rd question Kc value 9.09x10-3 answer mol-1 dm6
4th question electrophilic substitution
5th amino acid hydrolyse medical stitches
6 unsure
7 rate iodine h+ graph tangent r=k(H+)
8 8 marks for Naoh kcn hz Ni
9 molecular formula proof using empirical formula and that 9 marker 12 marks here

wat was question 6



this helps, i'll remake it in this format, might remember a few

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