AQA Chemistry Paper 2 AS Level 2016 Unofficial Mark Scheme

Actually think it was an alright paper, especially compared to paper 1.

Anymore answers are welcome and feel free to correct any mistakes. Thank you!

1.1 Kc=[product]/[Reactant 1][Reactant 2]
Unit- mol^-1dm^3

1.2 10.5 mol^-1dm^3

-Z-isomer (ignore my awful drawing, I tried doing it on my macbook)


-Equation for Cl free radical and ozone layer
Cl.+ O3 ---> ClO.+ O2
ClO.+ O3 ----> 2O2 + Cl.
-Drawing chloropentafluroethane

-Why those the molecule (one without Cl) not contribute to ozone depletion? Because doesn't have a C--Cl bond so no chlorine free radical is made.
-Why does greenhouse gases like Co2 absorb a lot IR? They have bonds that have high bond enthalpy

-Fluorine free radical and CH3CF2 (Check the formula I think it was that?)
Propagation Step 1: .F + CH3CF2 ----> .CH2CF2 + HF
Propagation Step 2: .CH2CF2 + F2 ---> CH2CF3 + .F

-Number of molecules + Avogadro constant question? 1.01 x 10^25

-Isooctane? Nomenclature- 2,2,4-trimethypentane
-Name how to separate Isooctane and octane and how?
Distillation and you heat the conical flask with temperature above 99 degrees so Isooctane compound vaporises but the other compound remains liquid. Condense in a cooling jacket.

-Oleic acid testing for unsaturated
Bromine water and Observation from orange to colourless

-Enthalpy change of Combustion of methanol- -307 kJmol^-1
-Why enthalpy change lower- neglecting the specific heat capacity of the calorimeter
-Uncertainty- 0.5/38*100= 1.32%
-Why Uncertainty of 0.5 is okay?
-Heat change for ethanol 11760 KJ maybe 11800KJ as it's in 3sf (I have a blurry memory about this one)

-Write the complete combustion of octane?
C8H18 + 12.5O2 -> 8CO2 + 9H2O
-Catalyst how it works
Lowers activation energy by providing an alternate route to a reaction
-How does NO and CO react?
2NO + CO ----> N2 + CO2
-Thin layer catalyst maybe because it's more cost effective and catalyst doesn't get used up during reaction so you don't need thick layer.

-Why are the two compound impossible to distinguish in precise mass spec?
Both has the same number of atoms for each element so same precise molecular mass.
-Infrared Radiation: O-H bond and 3230-3550 cm^-1

6 Marker: Alcohol (hydrogen bonds, permanent dipole dipole, van der waals) Aldehyde (permanent dipole dipole and van der waals) and alkane (van der waals)

7 Marker electrophilic addition
Outline Mechanism: arrow from double bon to H(delta plus) arrow from bond H---Br to Br)
Tertiary Carbonation ion is more stable than secondary carbocation because alkyl groups is electron releasing and stabilises the carbocation. So most stable carbocation is formed more. 3bromo is more stable than 2bromo.

-Excess find moles of both and magnesium has more moles than the other compound so more magnesium is needed for a the first compound to react.
-Graph- I drew it lower and slower because there's fewer moles of reactants. Should be lower and quicker according to other because the concentration increased.

-Acidified potassium dichromate display formula both ketone and carboxylic acid and equation

CH3CH(OH)CH2OH + 3[O] → CH3COCOOH + 2H2O

-Reflux Apparatus


-AntiBumping Granules

-What is the structure when not in excess?
Aldehyde and ketone one

Multiple Choices
-orange to red, aldehyde one with cho-
-Increase Temp- makes KC increase and yield increase C
-Last question multiple choice is C
-The C,H,O is B- ethanoic acid
-Nucleophilic Substitution
-Total Equilibrium moles 18
-The Cyclohexene general formula- CnH2n-2
-Cracking equation A
-Percentage yield is 86.6%
-Polymer question Which is the alkene- D
-Maxwell Graph- C That number of molecules of E>Ea
For the first 10 questions these may be the answers credit to @quiin f : CDDBAADCAB
Answers to 15 MCQ in order credit to @britishtf2 :
CDDABBDCABCDCBC

More answers
1) Students value inaccurate? Copper calorimeter absorbs heat
2) Catalyst: Lowerst Activation energy by providing alternative pathway for reaction
3)Mass spectrometry can't be used: Rounded figures are the same, and not accurate ro enough decimal places to distinguish
Multiple Choice:
C: CH3CHO
D: Nucelophilic Substitution
B: Mechanism picture
D: yield 86%
A: Sulfur dioxide removed in gas station
D: Repeating Polymer Methypropene
D: Maxwell Boltzmann Curve picture
A: Hexane question
B: Cn2n-2 formula
C: A+3B->C+2D gives 18 moles
C: Increase Temperature (yield of h2 an Kc)
B: 1064 missing enthalpy

Isn't the last MPC C and not D?

That first one, the question said to not mention heat transfer...
and for the third is not because of decimal places but because they have the exact same number of each element, they have the molecular formula to any decimal place

said heat transfer to the atmosphere

I personally said it heated the calorimeter, but I don't know.

davinci girl,

for the six marker about boiling points,

isnt it alcohol first as h bonding,

then the butane, because van der waals and has 4 carbon where as the prop-2-ene-1-one has 3 and dipole dipole force which is weaker thats what alot of my friends got and my teacher said it sounds right

yeah thats right i was talking about the fact that they said you cannot include heat transfer to the atmosphere which would exclude regular heat loss but calorimeter stil valid

yeah thats right i was talking about the fact that they said you cannot include heat transfer to the atmosphere which would exclude regular heat loss but calorimeter stil valid

The value of Kc was 5 point something, not 10....

For the Mass Spec one, isn't it that the 2 compounds had exactly the same number of each atom? And so even high res. mass spec. would result in the same Mr.?

More answers
1) Students value inaccurate? Copper calorimeter absorbs heat
2) Catalyst: Lowerst Activation energy by providing alternative pathway for reaction
3)Mass spectrometry can't be used: Rounded figures are the same, and not accurate ro enough decimal places to distinguish
Multiple Choice:
C: CH3CHO
D: Nucelophilic Substitution
B: Mechanism picture
D: yield 86%
A: Sulfur dioxide removed in gas station
D: Repeating Polymer Methypropene
D: Maxwell Boltzmann Curve picture
A: Hexane question
B: Cn2n-2 formula
C: A+3B->C+2D gives 18 moles
C: Increase Temperature (yield of h2 an Kc)
B: 1064 missing enthalpy

no it said dont meantion heat transfor to equipment

im pretty sure it was atmosphere but idk most people put the equipement as the answer so i dont think that would be the case

It did say atmosphere