Q12.
(a) Aldehyde/propanal has dipole-dipole forces (between molecules)
If any ‘covalent bonds broken’ CE=0 for clip.
Ignore Van der Waal forces
M1
Alcohol/propan-1-ol AND Carboxylic acid/ propanoic acid have hydrogen bonding (between molecules).
Ignore reference to energy
M2
The forces between the molecules in aldehyde are weaker (than those in alcohol and acid so it will evaporate first.)
M3 only awarded following correct M1 OR M2
Allow converse for M3
M3
(b) Keep the temperature of the reaction mixture below the boiling point of propan-1-ol/below 97 °C
Allow temperature in range 49-96 inclusive
Allow description of cooling the vessel
M1
Cool the distillate / collecting vessel
Ignore reference to oxidising agents
Penalise lid / sealed container
M2
(c) Add named carbonate/hydrogencarbonate OR magnesium to a sample of the distillate.
Incorrect chemical CE=0
Allow formula (mark on for incorrect formula)
Allow blue litmus or correct named indicator
M1
Effervescence/fizz/bubbles would confirm presence of acid or converse
Blue litmus turns red confirms acid present or converse
Allow gas/CO2 produced which turns lime water cloudy OR gas/H2 produced which burns with a squeaky pop
M2
(d) (Temperature difference = 15.1 °C)
If ∆T wrong – AE mark on otherwise can only award M2
If use 457 in M1, can only score M2
q = 150 × 4.18 × 15.1 or 9467.7 J or 9.4677kJ
M1
amount ethanol burned = 0.457/46.0 = 9.93 × 10-3 mol
If use 457 in M2 can score 2 for – 0.953 kJ mol-1
M2
Heat change per mole = (M1/1000)/M2 = 952.99 kJ mol-1
∆H = – 953 kJ mol–1 must be 3sfs and must be negative
(allow range -953 to -954)
BEWARE if they miss conversion to kJ and also miss
conversion to g, they get answer = – 953 which scores 1
+953 can score M1 and M2
Allow -950 or -960 for rounding to 2sf
M3
(e) Elimination
Penalise base elimination
M1
Mechanism : Either (E1)
M2 for protonation of alcohol, i.e. lp plus arrow to H+
or to H of H–O– in H2SO4 and from H-O bond to O
M3 for protonated alcohol plus arrow showing loss of
water
M4 for arrow showing loss of H+
From correct carbocation (E1)
wrong alcohol used / alkene formed loses M4
3
OR (E2)
M2 for protonation of alcohol, i.e. lp plus arrow to H+
or to H of H–O– in H2SO4 and from H-O bond to O
M3 for protonated alcohol plus arrow showing loss of
water
M4 for arrow showing simultaneous loss of H+
wrong alcohol used / alkene formed loses M4
3
(f) E-pent-2-ene
Allow trans
M1
C=C bond cannot rotate and
Each carbon in the double bond has (2) different groups attached.
Allow (two) different groups on each/either side of the double bond.
M2
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