O-LevelChemistryOrganic Chemistry5070/22 · May/June 2021 · Q910 Marks
The structure of ethyl propenoate is shown. H HO H H c=c-c—0—C—C—H H HH
- (a)Circle the atoms in the structure that show that ethyl propenoate is an ester.[1]
- (b)Aqueous bromine is shaken with a sample of ethyl propenoate. Explain, in terms of the structure of ethyl propenoate, why the aqueous bromine turns colourless.[1]
- (c)(i)Name the alcohol used in the reaction.[1]
- (c)(ii)The reaction uses an acid catalyst. State the effect of this catalyst on the position of equilibrium.[1]
- (c)(iii)The concentration of the alcohol is increased. Describe and explain what happens to the position of equilibrium.[2]
- (d)(i)Show that the maximum possible yield of ethyl propenoate is 15.0g.[3]
- (d)(ii)Calculate the percentage yield of ethyl propenoate in this experiment. % yield[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 2021). The mark or mark type is shown in brackets.
- [1] (circle) C-O-C=O
- [1] (reacts with the) carbon-carbon double bond
- [1] ethanol
- [1] no effect
- [1] moves to the right / moves to the side of the ester (1)
- [1] uses up the extra alcohol / to reduce concentration of alcohol (1)
- [1] mol of carboxylic acid = 10.8/72 OR 0.15 mol (1)
- [1] relative molecular mass of ester = 100 (1)
- [1] mass of ester = 0.15 × 100 (1)
- [1] 63 (%)
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