Aqa chem 4/ chem 5 june 2016 thread

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So I resat this paper (3rd year of A-Levels) and it's safe to say it's been a pointless 3 years considering I won't even get into university now :frown:

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your not alone :frown:

last chance hope I havent blown t would be so gutted

Reply 1341

Watafuk

Original post by FormlessBowl

30 ish marks lost given that everyone thinks it was the worst paper ever could be well into a B grade maybe even a Low A if youre lucky - so you can salvage it to an A* or an A.

The grade boundaries are likely to be their lowest ever since it was the hardest ever paper - try not to worry too much it was a ridiculous paper and everyone found it shocking

I domt think the grade boundaries will change that much (84 or 85 for a* imo) because the gorvernment thinks that too many people are getting a*s and a's.

Reply 1342

bat_man

question. you know part 8a.
I forgot what the last mark was for.
I put NaOH
Heat under reflux
then animal fats...? :s-smilie:

(i thought it was where could you find something similar to....idk tbh.

Reply 1343

lucifer9898

Original post by ELCRE

Guys would it be silly to make an official complaint to aqa? Some questions were just not fair such as the stitches one. Aqa are really playing with lives, they changed the wording and format of questions for the chem unit 2 paper (chucked in isa & Empa questions as well as one unit 5 question) & I let it go because I thought oh they mustve done it because its a resit paper but they have no excuse for this one.

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Yes make one! In 2010 I think Aqa did something very similar for the unit 4 biology exam. They also made a facebook page and everyone 'liked it'. Result: grade boundaries were very low!

Reply 1344

Ljm1998

The was a past paper previously that said the same sort of thing, the answer in this case is that it has polar regions eg C=O or whatever it was, and bacteria are able to digest those parts of the molecule and break it up, hence it will break off after some time which prevents pain and reopening of the wound from taking out the stitches early or poorly

Reply 1345

bluhbluhbuh

18:30- Updated- Version 2

18:12 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

Misc: tell me where these go!!!

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

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
E 2

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.

4.
Electrophile structure: CH3C(+)O

Reaction mechanism:
Arrow from benzene ring to C+ in CH3C(+)O, then arrow from hydrogen attached to the same carbon as the CH3CO back into the incomplete benzene ring (from carbon 1-4 i believe).

5. Can't remember exact questions, let me know i'll update ! =)
Notes:
Zwitterions have R-N(+)H3 and a COO-
Hydrogen bond between two amino acids: presumably show any partial bond from one hydrogen on one amino acid to either the nitrogen or oxygen on the other.
Dipeptides- essentially amides formed from 2 amino acids.

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.

7. Conc. Of propanone increases by 100, What is the new rate equation and explain pls:
rate = k[H+]Due to the large excess of propanone, it is no longer affecting the rate as only the H+ concentration limits the speed at which the reaction proceeds.

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. (?)

8. 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

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

Reply 1346

thehollowcrown

Original post by Ljm1998

But didn't it ask why the stitches with the polar bonds were better?

Reply 1347

FormlessBowl

Original post by Watafuk

I domt think the grade boundaries will change that much (84 or 85 for a* imo) because the gorvernment thinks that too many people are getting a*s and a's.

Theres absolutely no way they arent going down - theyve been saying too many people get the top grades for years and in the past few years hard papers have still resulted in lowered boundaries, this paper was as hard as they come.

Reply 1348

Ljm1998

Original post by Watafuk

I domt think the grade boundaries will chhange that much (84 or 85 for a* imo) because the gorvernment thinks that too many people are getting a*s and a's.

Aqa set their A*'s at 90% UMS, and after that the grade boundaries for an A are the total pupils scored below A* and find the 10% then again for BCand D, yet I will make a petition, where should I put it? Change.org? Or Facebook?

Reply 1349

Engineerrookie

Original post by lucifer9898

Yes make one! In 2010 I think Aqa did something very similar for the unit 4 biology exam. They also made a facebook page and everyone 'liked it'. Result: grade boundaries were very low!

You are a genius

Reply 1350

Funky-monkey

I'm really disappointed with how this exam has turned out. It turns out that learning all the content and doing all the papers isn't enough to do well in exams set by aqa anymore
Being asked random questions like the one about why you'd use the hydrochloride salt over the lidocaine doesn't do justice to those who worked hard and were doing well on papers like last year when there was a decent number of mechanisms and the questions actually made use of chemistry, rather than asking questions that have a tenuous link to chemistry

If the grade boundaries aren't low enough to reflect the ridiculousness of the paper, I really hope aqa feel shame, because they'll have denied some very capable candidates their rightful university choices, while those who did little work and got lucky end up getting the higher UMSs

You can still fix this, AQA
It's not too late
Make sure the grade boundaries reflect the difficulty of this exam

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Reply 1351

ELCRE

I still think we need to make a complaint to aqa even if nothing comes of it they need to know how badly they have messed us up. Someone was saying before theres no point doing that because we ALL had to sit the paper and we all answered the same questions. But the format & wording was completely different to anything we've ever seen before. The final question needed atleast 15 minutes to figure out which is way too much for a 9 marker. Terms used which we are not familiar with but were vital to understand so we could answer the question. TIMING was waay off, it took me 2-3 minutes to answer some of the one markers. There were questions that we spent days going over in class and practising but were replaced by stupid 1 markers about isotopes and percentage by mass. The list goes on.

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Reply 1352

Ljm1998

Original post by thehollowcrown

But didn't it ask why the stitches with the polar bonds were better?

Yes, same reasoning applies, polar regions mean bacterial enzymes can act Upton them and digest them into smaller parts, so the stitches, once healed the wound, disintegrate themselves sort of

Reply 1353

logicmaryam

The unofficial markscheme is coming together slowly. Vote in the poll!
http://www.thestudentroom.co.uk/showthread.php?t=4164897&page=3

Reply 1354

ishabennett

Can someone make a Facebook page. It's unfair because we haven't had the opportunity to practice that many application questions. If you want to test us on that then put it in past papers or resources online.

Reply 1355

Ljm1998

Let's start a petition or a group and get everyone who did this exam to join and support. Besides, the majority of the questions were short 1 mark and 2 mark answers but took too long to answer to be considered 1/2 marks, they deliberately made up waste time which is not fair, do not feel annoyed at yourself, no one wastes time, you went at your pace, no matter what pace you go at, no one loses 25 marks unless the paper was made to waste time. You should be angry at aqa

(edited 7 years ago)

Reply 1356

thehollowcrown

Original post by Ljm1998

Yes, same reasoning applies, polar regions mean bacterial enzymes can act Upton them and digest them into smaller parts, so the stitches, once healed the wound, disintegrate themselves sort of