AS-LEVEL PAPER 2 PP6 MS

1.   (a)     (i)      M1 c(oncentrated) phosphoric acid / c(onc.) H3PO4
OR c(oncentrated) sulfuric acid / c(onc.) H2SO4
In M1, the acid must be concentrated.
Ignore an incorrect attempt at the correct formula that is written in addition to the correct name.
M2 Re-circulate / re-cycle the (unreacted) ethene (and steam) / the reactants
OR pass the gases over the catalyst several / many times
In M2, ignore “remove the ethanol”.
Credit “re-use”.
2
(ii)     M1 
(By Le Chatelier’s principle) the equilibrium is driven / shifts / moves to the right / L to R / forwards / in the forward direction
M2 depends on a correct statement of M1
The equilibrium moves / shifts to
•        oppose the addition of / increased concentration of / increased moles / increased amount of water / steam
•        to decrease the amount of steam / water
Mark M3 independently
M3 Yield of product / conversion increase OR ethanol increases / goes up / gets more
3
(iii)    M1 Poly(ethene) / polyethene / polythene / HDPE / LDPE
M2 At higher pressures
More / higher cost of electrical energy to pump / pumping cost 
OR
Cost of higher pressure equipment / valves / gaskets / piping etc.
OR expensive equipment
Credit all converse arguments for M2
2
(b)     M1 for balanced equation
M2 for state symbols in a correctly balanced equation
2C(s / graphite) + 3H2(g) + ½O2(g)   CH3CH2OH(l)
(C2H5OH)
Not multiples but credit correct state symbols in a correctly balanced equation.
Penalise C2H6O but credit correct state symbols in a correctly balanced equation.
2

(c)    (i)      M1 The enthalpy change / heat change at constant pressure when 1 mol of a compound / substance / element
If standard enthalpy of formation CE=0
M2 is burned / combusts / reacts completely in oxygen 
OR burned / combusted / reacted in excess oxygen
M3 with (all) reactants and products / (all) substances in standard / specified states
OR (all) reactants and products / (all) substances in normal states under standard conditions / 100 kPa / 1 bar and specified T / 298 K
For M3
Ignore reference to 1 atmosphere
3
(ii)     M1
Correct answer gains full marks
ΣB(reactants) − ΣB(products) = ΔH
Credit 1 mark for (+) 1279 (kJ mol−1)

OR
Sum of bonds broken − Sum of bonds formed = ΔH
OR
B(C-C) + B(C-O) + B(O-H) + 5B(C-H) + 3B(O=O) (LHS)
− 4B(C=O) − 6B(O−H) (RHS) = ΔH
M2 (also scores M1)
348+360+463+5(412)+3(496) [LHS = 4719]
                         (2060)   (1488)
− 4(805) − 6(463) [RHS = − 5998] = ΔH
(3220)     (2778)
OR using only bonds broken and formed (4256 − 5535)
For other incorrect or incomplete answers, proceed as follows
•        check for an arithmetic error (AE), which is either a transposition error or an incorrect multiplication; this would score 2 marks (M1 and M2)
•        If no AE, check for a correct method; this requires either a correct cycle with 2C and 6H and 7O OR a clear statement of M1 which could be in words and scores only M1
M3
ΔH= − 1279 (kJ mol−1)
Allow a maximum of one mark if the only scoring point is LHS = 4719 OR RHS = 5998
Award 1 mark for +1279
Candidates may use a cycle and gain full marks
3
(d)    (i)      Reducing agent OR reductant OR electron donor
OR to reduce the copper oxide
Not “reduction”.
Not “oxidation”.
Not “electron pair donor”.
1
(ii)     CH3COOH
1
[17]

2.    (a)    M1 On the energy axis Emp at the maximum of the original peak
M1 The limits for the horizontal position of Emp are defined as above the word “the” in the sentence below the graph.
M2 The peak of their new curve is displaced to the left and higher than the original.
M3 All of the following are required
•        The new curve starts at the origin and should begin to separate from the original almost immediately
•        and the new curve crosses the original curve once
•        and an attempt has been made to draw the new curve correctly towards the energy axis below the original curve but not to touch the original curve or the axis
3
(b)     The rate of reaction decreases as the temperature decreases because
M1     A decrease in the number / proportion of molecules with E ≥ Ea
OR fewer molecules have E ≥ Ea
OR fewer molecules have sufficient / enough energy to react / decompose
In M1
Ignore “molecules have less energy”.
Ignore “less energetic collisions”.
Ignore “molecules do not gain activation energy”.
Ignore “fewer collisions”.
Credit “particles” for “molecules” but NOT “atoms”.
M2     Fewer effective / productive / successful collisions in a given time / given period
OR fewer frequent effective / productive / successful collisions
OR lower rate of effective / productive / successful collisions
Ignore “chance of collision”; this alone does not gain M2
2
[5]

3.     (a)     (i)      moles of C2F2 = 0.40   mark independently from HC1
1
moles of HC1 = 0.80   not consequential
1
(ii)     
         wrong Kc means they can only
         score for units in (iii) consequ
         on their Kc
1
(iii)     
1
         = 0.35
1
mol dm–3
1
(b)     (i)      increase
1
(ii)     decrease
1
(c)     addition or radical
1
[9]

4.     (a)               Type of alcohol: Tertiary (1)
Reason: No hydrogen atom on central carbon (1) 
2
(b)     (i)      Aldehyde (1)
Ignore named aldehydes or their structures,
penalise wrong named compound
(ii)     CH3CH2CH2CH2OH + [O] → CH3CH2CH2CHO + H2O (1)
Balanced (1)
C4H10O is OK as a reactant
[O] can be over arrow
C3H7CHO not accepted for product, but C2H5CH2CHO is OK
If use C3 or C5 compounds no marks in (ii) C.E of wrong alcohol
(iii)     Name Butanoic acid (1)
Structure: CH3CH2CH2COOH (1)
mark conseq. or as stated
5
(c)     Advantage: Fast reaction OR pure product OR continuous process
OR cheap on manpower OR high yield, 100% alcohol (1) 
Disadvantage: High technology OR ethene from non renewable source
OR expensive equipment not just costly (1)
Not answers based on fermentation
2
(d)     

4
[13]
 
5.     (a)     M1 curly arrow from lone pair on oxygen of hydroxide ion to
		H atom on C-H adjacent to C-Br
1
M2 curly arrow from single bond of adjacent C-H
to adjacent single bond C-C
(only credit M2 if M1 is being attempted to correct H atom)
1
M3 curly arrow from C-Br bond to side of Br atom
(credit M3 independently)
1

(b)    (i)      Ml curly arrow from middle of C = C bond to H atom on H-Br
(penalise M1 if partial negative charge or formal positive 
charge on H)
(penalise Ml if pent-2-ene is used)
1
         M2 curly arrow from H-Br bond to side of Br atom
1
M3 correct structure for correct secondary carbocation
1
M4 curly arrow from lone pair on bromide ion to the positive
carbon of carbocation, ensuring that bromide ion has a
negative charge.
(with the exception of pent-2-ene, if the wrong alkene is used, only penalise the structure M3)
(penalise the use of two dots in addition to a covalent bond, once only)
1
(ii)     1-bromopentane
1
(iii)     Ml 2-bromopentane is formed via the secondary (or 2°)
carbocation
1
OR 1-bromopentane is formed via the primary (or 1°)
carbocation
M2 a secondary carbocation is more stable than a primary
carbocation -
award this mark only if the quality of language justifies
the award.
(the argument must involve clear statements about carbocations)
1
[10]
 
6.	(a)		
	(b)		
	(c)		
	(d)		

	(e)		
	(f)		

	(g)		
	(h)		

7.	B
[1]
8.	D
[1]
9.	B
[1]
10.	C
[1]
11.	D
[1]
12.	C
[1]
13.	C
[1]
14.	D
[1]
15.	D
[1]
16.	C
[1]
17.	D
[1]
18.	A
[1]
19.	A
[1]
20.	A
[1]