O-LevelChemistryOrganic Chemistry5070/22 · Oct/Nov 2021 · Q410 Marks
Alkanes are a homologous series of hydrocarbons. The boiling point, melting point and density of alkanes increase as the number of carbon atoms increases.
- (a)(i)Give one other physical property of alkanes which increases as the number of carbon atoms increases.[1]
- (a)(ii)Give two other characteristics of a homologous series. 1 2[2]
- (b)Two typical reactions of alkanes are combustion and cracking. State the name of another typical chemical reaction of alkanes and the reactant needed to react with the alkanes. type of reaction reactant[2]
- (c)(i)State two conditions needed for cracking alkanes. 1 2[2]
- (c)(ii)Tridecane, C13H28, can be cracked to produce an alkene with four carbon atoms and one other hydrocarbon only. Construct an equation for this reaction.[1]
- (d)A hydrocarbon contains 88.9% carbon by mass. Calculate the empirical formula of this compound. empirical formula[2]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2021). The mark or mark type is shown in brackets.
- [1] viscosity
- [2] Any two from:
- similar chemical properties (1)
- same functional group (1)
- (have a) general formula (1)
- (successive) members differ by CH2 (1)
- [2] type of reaction: substitution (1)
- reactant: chlorine (1)
- [2] high temperature (1)
- catalyst (1)
- [1] C13H28 → C4H8 + C9H20
- OR
- C13H28 → 2C4H8 + C5H12
- OR
- C13H28 → 3C4H8 + CH4
- [2] C2H3 (2)
- if 2 marks not scored 1 mark for:
- C 88.9/12
- H 11.1/1
- OR 7.4 11.1 (1)
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