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AQA A Level Chemistry Paper 2 11th June Unofficial Markscheme

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I can't even remember what I put actually
Original post by Kpnuts2000
Was it pentan-2-one or something like that. I think I put 1 for a ketone and that doesn't even make sense.
yep
Original post by Spiker149
Was it Cyclopentanone?
Reply 82
Original post by jamesctu
does anybody know how to calculate this question


actual yield/ theoretical yield *100

it doesn't matter if yield is in moles or grams because moles = grams / Mr , and Mr is same top and bottom because it's the same compound, Mr cancels to give grams anyway.
What’s gb for an A* or an A on this paper do u think? Last year was 86 for an A*
Original post by ÷by0
Do you remember the exact question for mass spec? Was that the question where it was multiple compounds with the same molecular formula, or just same Mr? I do remember it saying "to the nearest whole number" but H, O, C, N etc, are all .0 on our data sheet, wasn't sure how many d.p in high.res.

It was the one that had the dioic acid in part 1 and the two diol isomers in part 2, or something, and the question asked why/how you could tell the dioic acid apart from the diols using high res mass spec. Them not being specific about the precision means use your imagination! Take the limit as the decimal places goes to infinity, ya feel? You can tell apart anything with a different molecular formula. (I've done a question where some high precision masses were given - it was something along the lines of of 4 d.p.)

The NMR isomer structures I did in the last 5 minutes of the exam, hated them.
I reckon for a A it will be a lot lower as the general consensus was everyone struggled
Original post by Mcgreggorrrrrrrr
What’s gb for an A* or an A on this paper do u think? Last year was 86 for an A*
Original post by Joe Furn
I reckon for a A it will be a lot lower as the general consensus was everyone struggled


Wb A*?
Original post by archibald300
Isn't NH4Br formed not HBr?

Yes! I said this. Molecule + 4NH3 —> 2NH2(Ch2)6NH2 + 2NH4Br
82
Original post by Mcgreggorrrrrrrr
Wb A*?
I reckon that will still be high but not as high as last year's. Or they may put it high so less people are getting A*s
Original post by Mcgreggorrrrrrrr
Wb A*?
For the CN ion condition I said ‘hot’

For the HCl I’ve said it’s harder to remove from the reaction mix and corrosive

Are those ok?
Original post by Edexcel Are mugs
82


What do u think u got on this paper?
Reply 92
which question was this for? was it value of k?
Original post by jakehill_01
it was 20000 to 3.s.f
yessir
Original post by ÷by0
which question was this for? was it value of k?
Original post by Gnuyheatmik
Tell me your answers so I can update this
I can’t really remember much

Equation 1,6-dibromohexane and excess ammonia

C6H12Br2 2 NH3 —-> C6H16N2 2 HBr
or
C6H12Br2 + 4NH3 —> 2NH2(Ch2)6NH2 + 2NH4Br (this is probably the correct equation but not sure)

Nucleophilic substitution skeletal formula with ammonia
Cyclic compound by-product
Cyclic compound was from the amino group nucleophilic.sub. on the bromine on the same molecule? reacts with itself.

Equation of ethanoic anhydride (hydrolysis? can't remember)
Forms Ethanoic Acid and Ethanol

Question about a compound and why it has no chiral carbon
No chiral centre because no carbon has 4 distinct groups attached

Explain the term Complementary in terms of DNA strands
Dna strands have complementary base pairs which are able to form hydrogen bonds between them

Draw hydrogen bonds between the strands
3 bonds between C and G
2 bonds between A and T

Circle the components that make up the nucleotide with cytosine
3 Circles around:
Phosphate group, 2-Deoxyribose, Cytosine

Vegetable Fat Question with CxHy

Initial Rates
3.2 x 10^-4
3.2 x 10^-4
First order
Second order

Bunch of numbers I can remember
1.39
182kg
20000
2.57 x 10^9 Arrhenius
28.5% percentage yield
units mol-3 dm9 s-1

Diagram Distillation apparatus
Add condenser and thermometer

Hydrolysing proteins
HCl or NaOH debate about his one

Labelling infrared spectrum F,G,E can’t remember the order
Ester at top (bc no OH peak), then alcohol, then, carboxylic acid.

6 marker on the 2 different compounds (one was a cyclic ketone the other was an alcohol)
-boiling points
Hydrogen bonding in one of them stronger than dipole forces
-Cnmr
-infrared spec

CO2 how does it cause global warming
C=O absorbs IR (heat radiation). Absorbs this energy / retains heat / increases temp of gas (guessing for the second mark).

Minimum number of amino acids in mixture
7

How to see the amino acids
Fluorescent dye and UV/Ninhydrin

How can they tell if the sample has dried by adding anhydrous calcium something ...
Drying cyclohexane makes the solution turn clear ?

The weird question on Z,Z adding the carbons to a skeletal formula
Z,Z, skeletal formula has double bond between 9/10 and 12/23. Z same side, so chain curls

Name mechanism with benzene
Electrophilic substitution

Reaction with bromine finish off the mechanism
- electrophilic addition forming carbo cation then the second bromine ion adds on. Forms dibromo...

Distinguishing between primary and tertiary alcohol
Add acidified potassium dichromate
Orange --> Green
No Change

Last question about nucleophile not being able to attack an Alkene.
I think it’s either:
C=O is polar so the nucleophile can attack the partially positive carbon. The alkene doesn’t have a C=O group so not polar so can’t be attacked by nucleophile.
OR
The nucleophile repels the double bond in the alkene

Insufficient NaH4B added. Test for aldehyde
Add tollens/fehlings
Silver mirror/red ppt

Molecular/Emperical formula question
C5H8 you had to times by 5 to get a whole number
Structure was a branched monomer, e.g H2C=C(CH3)--CH=CH2

Formula of the dicarboxylic acid with an Mr of 118
HOOC- (CH2)2 -COOH

Draw two structures for C6H3Br3
One with One peak in C nmr
One with 4 peaks in C nmr
Benzene ring/kekule structure (several correct answers for this one)
D with 4 peaks on 13C spectrum was 1,2,3-tribromobenzene - C2,C3,C4,C5 symmetrical same as C2,C1,C6,C5

Synthesis question
Nitrobenzene to amine equation finish off equation
Add 6[H] to form 2H2O

Reagents for the reduction of nitrobenzene
Reagents are H2 and Ni (more than one correct answer for this one)

Reagents and conditions for 2 step synthesis to form an amine
KCN aqueous ethanolic
Sn/HCl (think there is more than one correct answer for this one)

Why does stereoisomerism occur
Restricted rotation around C=C bond. Higher priority groups on same or opposite sides of the double bond.

Draw isomers for golf ball
Don't degrade because no polar bonds, so not susceptible to nucleophillc attack.

Isomer of C4H8Br2 with 2 singlet peaks on 1H spectrum
Structure was C(CH2Br)(Br)(CH3)2

How does high-res mass spec differentiate molecules with Mr = 118? - electro spray adds H increasing mass.
Higher precision will distinguish between them because they're the same to the nearest whole number

Why would it be better to use anhydrides rather than acyl chlorides?
Don't use acyl chlorides because toxic HCl fumes/ reacts violently - irritant / acid raid.

IUPAC Names
Buta-1,3-diene
Cyclopentanone
Ethyl Propanoate


Isn’t using acyl chloride more expensive as a reason?
And we weren’t asked for the reagents for reduction of nitrobenzene???
I thought CN would have to be stated as reflux?
Yeah I put corrosive as well - I think that's ok!
Original post by phosphene
For the CN ion condition I said ‘hot’

For the HCl I’ve said it’s harder to remove from the reaction mix and corrosive

Are those ok?
That's what I put
Original post by Spiker149
Was it Cyclopentanone?
Original post by Lucallah
It was the one that had the dioic acid in part 1 and the two diol isomers in part 2, or something, and the question asked why/how you could tell the dioic acid apart from the diols using high res mass spec. Them not being specific about the precision means use your imagination! Take the limit as the decimal places goes to infinity, ya feel? You can tell apart anything with a different molecular formula. (I've done a question where some high precision masses were given - it was something along the lines of of 4 d.p.)

The NMR isomer structures I did in the last 5 minutes of the exam, hated them.

do you know how to do this question
Reply 98
Do you know what number question that was in the book?
Original post by jamesctu
do you know how to do this question
4.2
Original post by ÷by0
Do you know what number question that was in the book?

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