Topic 11 Practice Paper: Organic chemistry — mark scheme (print)

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QQ/IGCSE-CHEM/T11

IGCSE · Cambridge IGCSE Chemistry (Extended (Core + Supplement))

Mark scheme

Organic chemistry

Topic 11 Practice Paper · Maximum mark: 30

Notes for markers

Award one mark for each point marked [1], up to the marks shown for the part.
Accept answers worded differently that show the same understanding.
Units are required where the answer line shows one. ecf: allow an error carried forward.

Section A: Multiple-choice questions[10 marks]

Question	Answer
1	BThe –COOH group identifies a carboxylic acid. CH₃OH is an alcohol, CH₃COOCH₃ an ester and C₂H₄ an alkene.	1
2	CCracking breaks molecules apart after separation; the tower itself sorts hydrocarbons by boiling point.	1
3	ASingle bonds only, hence saturated and unreactive — which is why the bromine colour survives and the double-bond statements are false.	1
4	DBitumen has the longest chains, the highest boiling points and the greatest viscosity, so it collects at the base.	1
5	AA nickel catalyst is specified for the hydrogenation of alkenes; silica or alumina catalyses cracking and yeast drives fermentation.	1
6	CComplete combustion of any hydrocarbon or alcohol yields carbon dioxide and water; carbon monoxide signals incomplete burning.	1
7	DCarboxylic acids behave like other acids with carbonates: a salt (an ethanoate), water and carbon dioxide.	1
8	BAn ester forms when the alcohol (ethanol) reacts with the carboxylic acid (ethanoic acid) over an acid catalyst.	1
9	CUp the column molecules are shorter, so they boil lower, evaporate more readily and flow more easily.	1
10	DPET, a condensation polyester, can be depolymerised to its monomers and made into new polymer — unlike nylon, proteins or addition plastics.	1

Section B: Structured questions[20 marks]

Question	Answer and marking points	Marks
11(a)	M is unsaturated; the rapid loss of the bromine colour shows a carbon–carbon double bond, so M is an alkene. M identified as unsaturated [1] alkene [1]	2
11(b)	The colour remains, because L is saturated: all its carbon–carbon bonds are single, so no rapid addition of bromine can occur. colour stays orange-brown [1] saturated / only single bonds [1]	2
11(c)	Carbon monoxide and particulates (soot). [1]	1
	Total for Question 11	5
12(a)	ethanol + oxygen → carbon dioxide + water [1]	1
12(b)	Fermentation: yeast is added to an aqueous glucose solution and kept at 25–35 °C in the absence of oxygen; the yeast enzymes convert the glucose to ethanol and carbon dioxide. yeast [1] 25–35 °C [1] no oxygen / anaerobic [1]	3
12(c)	Alcohols; the –OH (hydroxyl) group. alcohols with –OH group [1]	1
	Total for Question 12	5
13(a)	But-1-ene and but-2-ene. but-1-ene [1] but-2-ene [1]	2
13(b)	structural isomers [1]	1
13(c)	Add orange-brown aqueous bromine; it is decolourised quickly because each molecule adds bromine across its double bond. aqueous bromine added [1] decolourised rapidly [1]	2
	Total for Question 13	5
14(a)	A monomer is the small molecule that is joined repeatedly; a polymer is the large molecule built from many monomer units. monomer = small repeating starting molecule [1] polymer = large molecule of many linked monomers [1]	2
14(b)	addition polymerisation [1]	1
14(c)	Any two of: filling landfill sites; accumulating in oceans and harming marine life; releasing toxic gases when burned. two valid problems [2]	2
	Total for Question 14	5

— End of mark scheme —