AQA A Level Chemistry Paper 2 11th June Unofficial Markscheme

Original post by jamesctu

do you know how to do this question

((2x10-2)-(1.84x10-2))/5

((0.5x10-2)-(0.34x10-2))/5

Reply 102

Zaki1039

i drew the structure of a dipeptide and looked at what groups would reform (NH2 and COOH) so i decided that water could be used but im not sure if this is correct

Original post by Lucallah

First Google result says NaOH can't be used to hydrolyse proteins as it breaks down the amino acids, so I'm pretty sure that would be wrong. Using HCl is the process included in the spec but the equation only shows H+ so I feel like the choice of acid isn't too important.

Reply 103

I wrote water too. Mainly because hydro was in the name, but also because peptides/polyamides are susceptible to nucleophilic attack from water - this is what makes them biodegradable. So i figured that this may be suitable, because hydrolysis of ester is done by adding water.

I think the main purpose of the acid or alkali is to act as catalyst. I don't remember how many marks the question was, so i don't know if you needed to say both, or with water being amphoteric is enough.

Original post by Zaki1039

i drew the structure of a dipeptide and looked at what groups would reform (NH2 and COOH) so i decided that water could be used but im not sure if this is correct

Reply 104

jamesctu

Original post by 0rg4n1c

((2x10-2)-(1.84x10-2))/5

((0.5x10-2)-(0.34x10-2))/5

H i friend do you know how to answer this question

Original post by jamesctu

H i friend do you know how to answer this question

Convert Ea to J.
Convert T into Kelvin.
Plug into equation and rearrange for A.

I have just started a new thread called A-level Chemistry Paper 2 - Exam Topics / Questions https://www.thestudentroom.co.uk/showthread.php?t=5997186 to streamline the unofficial mark scheme answers. If you remember specific questions i would really appreciate it if you could post them there, and I will do my best to answer any questions you have :smile:

Reply 106

jamesctu

Original post by ÷by0

Convert Ea to J.
Convert T into Kelvin.
Plug into equation and rearrange for A.

I have just started a new thread called A-level Chemistry Paper 2 - Exam Topics / Questions https://www.thestudentroom.co.uk/showthread.php?t=5997186 to streamline the unofficial mark scheme answers. If you remember specific questions i would really appreciate it if you could post them there, and I will do my best to answer any questions you have :smile:

how do you rearange it
i converted t into 298k
ea into 96200 J
k=3.46 x 10-8
r=8.31

Reply 107

so far based on paper 1 and 2 difficulty, what do you think the grade boundaries potentially will be? Was 204 for an A in 2017 but those papers were easier than 2018 which was 198 for an A.

Reply 108

lily Spence

Why did I get like 136% or something for the yield I assumed impurities wow I really messed this one up

Reply 109

Gnuyheatmik

OP

Original post by Utd4life0101

so far based on paper 1 and 2 difficulty, what do you think the grade boundaries potentially will be? Was 204 for an A in 2017 but those papers were easier than 2018 which was 198 for an A.

Not sure but I imagine lower than last year. Probably not by much. 79-80% for A* 65-67% for an A. That’s just my guess though depends on paper 3 as well

Reply 110

Original post by jamesctu

how do you rearange it
i converted t into 298k
ea into 96200 J
k=3.46 x 10-8
r=8.31

Work out the value for e^-(Ea/RT) which is just a number, lets say that = x, which you can store in your calculator. You now have k=Ax, => A = k/x.

Reply 111

yeah hopefully. any predictions for paper 3? and for mcqs any advice?

Original post by Gnuyheatmik

Not sure but I imagine lower than last year. Probably not by much. 79-80% for A* 65-67% for an A. That’s just my guess though depends on paper 3 as well

Reply 112

jamesctu

do you know what the answer was friend

Original post by ÷by0

Work out the value for e^-(Ea/RT) which is just a number, lets say that = x, which you can store in your calculator. You now have k=Ax, => A = k/x.

Reply 113

2.57x10^9 s-1

Original post by jamesctu

do you know what the answer was friend

Reply 114

for the nucleotide components of cytosine, did you need to circle the cytosine as well? i thought it said the other components that make it up... 2-deoxyribose etc and it wouldve overlapped with my hydrogen bonds.

Reply 115

I thought the question asked you to circle the components that make up the nucleotide containing cytosine. nucleotides do have 3 components, but cytosine was stated in the question. Tbh, I'm not a biologist so i don't really know.

Original post by Utd4life0101

for the nucleotide components of cytosine, did you need to circle the cytosine as well? i thought it said the other components that make it up... 2-deoxyribose etc and it wouldve overlapped with my hydrogen bonds.

Reply 116

Gnuyheatmik

OP

Original post by Utd4life0101

yeah hopefully. any predictions for paper 3? and for mcqs any advice?

not really sure what will be on it tbh. i doubt there will be many organic practicals as there were a few today. electrochemical cells will definitely be on as it hasnt been on any of the papers so far. for mcqs i just do loads of practise questions in timed conditions

Reply 117

naimahh14

3

guys -
how did people work out the molecular formula for the golf ball question ?

Reply 118

in total how many marks do those nmr one/two markers add up to?

Reply 119