AS-LEVEL PAPER 2 PP17 MS

1.     (a)     SF6 shown as octahedral / square based bipyramid (1)
Bond angle: 90° or 180° and 90° (1)
Shape = octahedral (1)
If lone pair shown then C.E. = 0 / 4

Wrong symbols ‑ no diagram mark
          Equal repulsion between 6 bonding or shared electron pairs QoL (1)
AlCl4– shape shown as tetrahedral (1)
Bond angle = 109° to 109.5° (1)
Shape = tetrahedral (1)
If lone pair shown then C.E = 0/4

(Equal repulsion between) 4 bonding pairs or shared electron pairs (1)
QoL may be awarded here also
Mark all points independently
8
(b)     Solvent has low bp or weak intermolecular forces or evaporates quickly (1)
(Solvent) needs energy to evaporate (to overcome intermolecular forces)
or valid reference to latent heat of vaporisation (or evaporation is
endothermic) (1)
OR higher energy or faster molecules more likely to escape
so mean energy (and hence temperature) falls
          Energy taken from the skin (and so it cools) (1)
          Fragrance or perfume (molecules) slowly spreads (through the room) (1)
          By random movement or diffusion (of the perfume / fragrance) (1)
4
[12]
 
2.       (a)     Increase in temperature:
          Yield is increased (Allow if for H2 (g) or products) (1)
Reaction endothermic (1)
Equilibrium moves to the right OR forward, OR Equilibrium moves to
oppose change OR to absorb heat (1)
If “Yield statement” incorrect allow max one if reaction stated to be endothermic
Increase in pressure:
Yield is decreased (Allow if for H2 (g) or products) (1)
Increase in moles of gas or 2 moles increased to 4 moles or more moles
on right (1)
Equilibrium moves to the left OR backwards, OR Equilibrium moves to
oppose change OR to reduce pressure (1)
If “Yield statement” incorrect allow max one if number of moles change is correct.
6

(b)     Equilibrium yield:
Unaffected or equilibrium unchanged (1)
Rate or speed increased (1)
Forward and backwards reactions equally or by the same amount (1)
Amount of hydrogen produced:
More hydrogen produced (1)
4
[10]
 
3.	

4.      (a)     (i)      A molecule/compound/it consists/it is composed/it is made up of
hydrogen/H and carbon/C only (1)
QoL
(ii)     release (heat) energy (when burned) (1)
OR provides a (useable form of) energy
OR is a source of energy
Accept heat  energy
NOT is energy / is heat
NOT burns exothermically
(iii)     C4H10 + 6½O2 → 4CO2 + 5H2O (1)
OR 2C4H10 + 13 O2 → 8CO2 + 10H2O
ignore state symbols
(iv)    C4H10 + 4½O2 → 4CO + 5H2O (1)
OR 2C4H10 + 9O2 → 8CO + 10H2O
ignore state symbols
(iii) and (iv) if not C4H10 = CE
(v)     Limited or reduced supply of air / oxygen (1)
OR low temperature OR poor mixing
OR insufficient oxygen / air OR shortage of O2
NOT no oxygen / lack of oxygen / not in excess
5
(b)     (i)      C2H6 / CH3CH3 → CH2=CH2 / H2C=CH2 / C2H4 + H2 / CH2CH2
NOT CH2.CH2
(ii)     Al2O3 OR Zeoli(y)te OR aluminosilicate (1)
NOT bauxite
ignore SiO2
NOT Aluminium Silicate
NOT porous pot
NOT SiO2 alone
(iii)     More useful / needed fuels / products OR implied
OR more valuable products
OR qualified demand exeeds supply
OR to produce motor fuels OR petrol OR cycloalkanes OR aromatic hydrocarbons OR balanced alkanes OR smaller molecules OR alkenes
3
[8]

5.          (a)     CH4 + 2O2 → CO2 + 2H2O
Accept multiples
Ignore state symbols even if incorrect
1
Not enough oxygen / air
1
CMM / methane is a greenhouse gas / contributes
to global warming
Do not allow formation of CO2 / CO2 is a greenhouse gas
Apply list principle, eg
CH4 is a greenhouse gas and toxic = 0
CH4 is a greenhouse gas and damages ozone = 0
Allow CH4 and CO2 are greenhouses gases
Allow collect to use as a fuel so fossil fuels do not run out (as quickly)
1

(b)     CH3SH + 3O2 → CO2 + 2H2O + SO2
Accept multiples
Ignore state symbols even if incorrect
1
Calcium oxide is basic (and SO2 is acidic) /
CaO neutralises SO2 /
CaO reacts with SO2 to form gypsum / salt / solid /
CaSO4 / CaSO3
Allow CaO + SO2 → CaSO3
M2 and M3 can only be scored if SO2 seen somewhere in the answer
1
Acid rain
Allow consequence of acid rain eg increased rusting of iron / fish in lakes die / problems for asthmatics
Apply list principle
Ignore air pollution
1
[6]
 
6.          Penalise missing • once only
(i)      Cl2 → 2 Cl• (1)
(ii)      CH2Cl2 + Cl2 → CHCl3 +HCl (1)
(iii)     CH2Cl2 + Cl• → CHCl2• +HCl (1)
CHCl2• +Cl2 → CHCl3 + Cl• (1)
Can reverse order
(iv)     Effect on rate: increases (1) If decrease given C.E zero marks
Explanation: more Cl• radicals formed (1)
More Cl atoms, more Cl—Cl or Cl2 bonds broken, more Cl2 have
EA, increased rate of Cl• production
[6]
 
7.	(a)	

	(b)		
	(c)	[7]	
8.	

9.	(a)     For 2 marks at least one correct reference either to Mr or value to 5
decimal places required
QoL (associated with the bold statement here)
M1  Compounds 1 and 3 (butanal and butanone) have the same Mr (to 5dp)
        because either
It may be possible to award 2 marks if there is a clear statement about oxygen having a different precise Ar in the context of the comparison
•    they contain the same number of atoms of the same / each element
•    are both C4H8O
•    have the same molecular formula
NB The word “similar” does not mean “the same”
•    contain the same number of C, H and O atoms
M2  Compound 2 (pentane) has a different Mr (to 5dp) because either
•    it has different numbers of atoms of different elements
•    is C5H12 / only contains C and H
•    different molecular formula
•    does not contain oxygen (atom) / C=O
2
(b)     WithTollens’ (reagent)
M1 silver mirror
OR black solid/precipitate
(NOT silver (mirror) precipitate)
M2 (stays) colourless
OR no change / no reaction
OR no silver mirror
With Fehling’s (solution)
M1 Red solid/precipitate
(Credit orange or brown solid)
M2 (stays) blue
OR no change / no reaction
OR no red solid
OR no (red) precipitate
N.B No mark is awarded for the reagent
If no reagent given allow 1 mark for a consistent statement of M1 and M2
For M2, ignore “nothing (happens)”
And ignore “no observation”
2
[4]

10.   (i)      More absorption/less transmittance of infrared radiation
by it/water vapour
OR broader absorption by OH
OR less absorption/more transmittance of infrared radiation
       by carbon dioxide
Must be comparative
This may be described and must not be contradictory
Credit answers which refer correctly to “transmittance”
(more absorption = less transmittance)
1
(ii)      M1    CO2 contains C=O (stated like this or in words or strongly
implied) OR is O=C=O
M2    depends on correct M1
OR expected absorption/peak (for C=O) is missing
OR expected absorption/peak (for C=O) is shifted to 2300 (cm–1)
OR asymmetric stretching is occurring (due to C=O)
If M1 and M2 not scored, give one mark for either
No absorption/peak at 1700 (cm–1)/1715 (cm–1)
OR no absorption in the range 1680 – 1750 (cm–1)
Ignore “carbon-oxygen bonds”, “C-O bonds”
Ignore reference to other absorptions
For M2
Allow “dip” OR “spike” OR “low transmittance” as alternatives for absorption.
2
[3]
 
11.  (a)     ‘Initial mass’ must be the y-axis
	If axis unlabelled, use data to decide that ‘Initial mass’ is on the y-axis.
1
Sensible scale
Do not award this mark if plotted points do not cover at least half of the grid.
Do not award this mark if any plotted point is outside the grid.
1
All points plotted correctly
Allow ± one small square.
1
Point at (0,0) is ringed
1
(b)     Best-fit straight line that goes through the origin ± ½ small square
Mark consequentially to plotted points but the line must still go through the origin ± ½ small square.
Lose this mark if the line is doubled or kinked.
If the points are plotted correctly, lose this mark if the line deviates towards the anomalies.
1
(c)     Students 3 and 5
Allow masses of 1.15 and 1.53 or 2.82 and 3.58
Mark consequentially to plot.
1
(d)     Samples 3 or 5 have not lost all their water
Allow reaction / decomposition incomplete.
1
Sample not heated for enough time / larger masses will take a longer time to dehydrate / decompose
1
[8]