O-LevelChemistryOrganic Chemistry5070/22 · May/June 2023 · Q710 Marks
Ethene, but-1-ene and but-2-ene are alkenes. The displayed formulae of ethene and but-1-ene are shown in Fig. 7.1. [Figure 7.1]
- (a)State the general formula of the homologous series of alkenes.[1]
- (b)(i)But-1-ene and but-2-ene are structural isomers. State the meaning of the term structural isomers.[1]
- (b)(ii)Draw the displayed formula for but-2-ene.[1]
- (c)(i)But-1-ene is an unsaturated hydrocarbon. State why but-1-ene is an unsaturated compound.[1]
- (c)(ii)State why but-1-ene is a hydrocarbon.[1]
- (d)(i)But-1-ene reacts with steam in the presence of a catalyst and reacts with bromine. Draw the structural formula of the product of the reaction with steam in the presence of a catalyst.[1]
- (d)(ii)Draw the structural formula of the product of the reaction with bromine.[1]
- (e)(i)Ethene is a covalent substance. Draw a dot-and-cross diagram to show the bonding in a molecule of ethene. Include only the outer shell electrons of each atom.[2]
- (e)(ii)Explain why ethene has a low melting point.[1]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.
- 7(a) CnH2n (1)
- 7(b)(i) same molecular formula but different structural formula (1)
- 7(b)(ii) ΗΗΗΗ / H—C—C=C—C—H / H H (1)
- 7(c)(i) contains a double bond between carbon atoms (1)
- 7(c)(ii) contains only carbon and hydrogen (1)
- 7(d)(i) CH3CH2CHOHCH3 / CH3CH2CH2CH2OH (1)
- 7(d)(ii) CH3CH2CHBrCH2Br (1)
- 7(e)(i) double bond between C—C shown (1)
- each carbon to have two C—H bonds shown (1)
- 7(e)(ii) weak intermolecular forces (1)
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