F324 TEST 3 MARK SCHEME
1.	(a)	Rf value is distance moved by a component/spot/solute divided
by distance moved by solvent. (1)
	Retention time is the time between injection and emergence
(or detection) of a component. (1)	2
(b)	(i)	Partition / adsorption (1)	1
(ii)	Role of gas: carrier gas / mobile phase / to carry to sample
through the chromatography column (1)
	Role of liquid: stationary phase (1)	2
(iii)	Trace with two peaks drawn (1)	1
(iv)	Measure area under each peak (1)
	Find total area (1)
	% = (area of one peak/total area) × 100% (1)	3
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2.	(i)	A C3H6 (1)	B C4H8 (1)	2
(ii)	A CH3CH=CH2 (or displayed) (‘sticks’ penalised once)	1 
(iii)	C3H5+ (1) for formula and (1) for charge	2
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3.	(a)	(i)	Molecular ion peak: the peak caused by the unfragmented
molecule / the peak with the highest m/e value / the peak
that tells you the Mr.	1
	Base peak : peak with the greatest (relative) intensity /
peak representing most stable/abundant fragment
NOT the tallest / biggest / most common peak	1
(ii)	The molecular ion is too unstable / will have been
completely fragmented / may not carry a positive charge	1
NOT peak too small to be seen / too little ion present
(b)	IR spectrum:
C=O peak at approx 1650 cm–1 (1680-1750 cm–1)	1
broad O-H peak at value(s) between 2500-3300 cm–1	1
ignore any references to C-O peak at 1000 – 1300 cm–1
	mass spectrum:
Fragment with m/e = 31 is CH2OH+	1
Fragment at m/e = 45 is COOH+	1
	penalise missing + sign once only

(c)	2 proton peak at δ = 3.3-4.3 – singlet (-CH2-)	1
1 proton peak at δ = 1.5-5.5 – singlet (-OH)	1
1 proton peak at δ = 11.0-11.7 – singlet (-COOH)	1
(ranges of chemical shift (δ) values taken from data sheet)
•	penalise each error once only
•	ignore peak areas/heights unless incorrectly labelled
	Labelled diagram of the structure of G proposed by the student
may be used to provide evidence for the positioning of peaks
on the sketched spectrum.
	Both OH and COOH protons disappear on shaking with D2O	1
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4.	(a)	(i)	Find the m /e of …. (1)
... the peak furthest to the right / with highest m /e or mass (1)	2
allow attempts to cater for the 13C peak
	C2H3O2 /empirical formula has Mr = 59 (1)
so Mr of molecular formula is 118/59 = 2 /twice the empirical formula (1)	2
(b)	(i)	OH peak disappears (with D2O / on the second spectrum)	1

(iii)	no of peaks: one (1)
	splitting: none (1)
	all four protons equivalent / in the same environment (1)	3
if the wrong structure is chosen allow ecf for:
two peaks (1),
splitting (1)(1) (as last 2 marks for part (ii))
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