The Student Room Group

OCR Chemistry A 2016 unofficial mark scheme 27/05/16

Scroll to see replies

Original post by SGHD26716
I know this is unlikely that you remember this but do you know the equation and moles. I just can't remember the answer I wrote if it was right or not.

dk if this is the right question but
2:1 ratio
0.075 mol
so 0.15 mol


guys I remember some multi choice questions i doubt anyone cares or not, either way:

- shape around carbon atoms in graphene
- iodoalkane hydrolysing fastest
- calculating enthalpy of formation using enthalpy of combustion - i got -129
- which skeletal formula oxidised to a ketone (near the end) - B??
- which molecule was non-polar - E 2,3but-2-ene

if anyone remembers them pls say there was 20.
(edited 7 years ago)
Reply 81
How did you do the enthalpy change of reaction question
Original post by Bosssman

Empirical formula with water of crystallisation: Cr3Cl 6H2O


It was CrCl3•6H2O, wrong way round!
Reply 83
Have a feeling the grade boundaries are going to be pretty high as the paper was decent.. Next one is going to be a lot more technical. How did everyone find the one today
Reply 84
Original post by tamoni4
You cannot use Br2 because you will make a dihaloalkane and you cannot make an alcohol from dihaloalkane. You had to use HBr to make haloalkane and then NaOH to make alcohol.


It had two OH groups so you had to use Br2 or Cl2
Original post by lauren1346
It was CrCl3•6H2O, wrong way round!


I got this but I didn't even put the dot in between😒 they're probably going to mark it wrong


Posted from TSR Mobile
What did you put for the iodoalkabe hydrolysing the fastest.
@alkaline.
(edited 7 years ago)
Reply 87
Original post by medicapplicant
What did you put for the iodoalkabe hydrolysing the fastest.
@alkaline.


C-I bond requires less energy to break
Original post by MsDanderson
I got this but I didn't even put the dot in between😒 they're probably going to mark it wrong


Posted from TSR Mobile


Based off of the new mark schemes they are very... anal. So sadly I think you'll drop 1 mark. :frown:
Original post by Bosssman
C-I bond requires less energy to break


Alright good and I swear that water of crystallisation question answer was CrCl3.6H20 like someone above
Reply 90
Original post by medicapplicant
Alright good and I swear that water of crystallisation question answer was CrCl3.6H20 like someone above


Maybe, there was a 3 somewhere and the other element was 1 and the water was 6
Original post by Bosssman
I don't have a copy of the exam, literally just walked out of the exam room 30 mins ago haha


what calc do you have
Original post by Bosssman
Maybe, there was a 3 somewhere and the other element was 1 and the water was 6

ya it was i think CrCl3 . 6H20
Reply 93
Original post by MsDanderson
I got this but I didn't even put the dot in between😒 they're probably going to mark it wrong


Posted from TSR Mobile

They did explicitly say to 'show clearly the water of crystallisation'
Original post by connorhill
Anyone tell me how they got 58 or whatever it was for the enthalpy change, I got the 4... KJ then I think I divided it by like 0.174 to get 19?


I got -19.5 ... Didn't you have to times the number of moles by three?
Reply 95
Hated that paper! Wasn't the 10% more-find concentration question 2 marks not 3. How many marks do you think you lost?
Reply 96
Original post by alkaline.
dk if this is the right question but
2:1 ratio
0.075 mol
so 0.15 mol


guys I remember some multi choice questions i doubt anyone cares or not, either way:

- shape around carbon atoms in graphene
- iodoalkane hydrolysing fastest
- calculating enthalpy of formation using enthalpy of combustion - i got -129
- which skeletal formula oxidised to a ketone (near the end) - B??
- which molecule was non-polar - E 2,3but-2-ene

if anyone remembers them pls say there was 20.

I think there are always 20 marks available in MCQ. Shape around graphemes, I put tetrahedral.
Original post by SGHD26716
I think there are always 20 marks available in MCQ. Shape around graphemes, I put tetrahedral.


I thought it was tetrahedral bc that's just generally what it is in alkanes
Ive realised now that in graphene each carbon is bonded to 3 other carbons and theres one free floating or something so idk if it's trigonal planar ... ://

upon googling: http://virtuallaboratory.colorado.edu/CLUE-Chemistry/chapters/chapter3txt-3.html
"This geometry is called trigonal planar and the C–C–C bond angle is 120°"

fuc.
Original post by Bosssman
Maybe, there was a 3 somewhere and the other element was 1 and the water was 6


I googled both, Cr3Cl.6H2O doesn't seem to be a thing, whereas CrCl3.... does.
I think i got a B on the paper and not quite the A grade. What marks will i need in the next paper (Depth) to get an overall A grade for AS Chemistry.

Quick Reply

Latest