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Esterification and naming esters — Free MYP4 Chemistry Practice Questions
1QuestionProperties: Pleasant smell and VolatilityConcept Practice
2 marks~3 minCriterion A
The structural formula of ethyl ethanoate is shown below.
[Structural formula diagram]
[Structural formula diagram]
a
State the IUPAC name of the small molecule eliminated when ethanol and ethanoic acid undergo a condensation reaction to form ethyl ethanoate. [1]
b
Explain how concentrated sulfuric acid increases the yield of ethyl ethanoate in this reaction. [1]
Solutions
2QuestionUses: Perfumes and Food flavoringAssessment Practice
3 marks~5 minCriterion D
The graph below shows the hydrolysis of ethyl ethanoate () at three pH values over time. The y-axis shows ester concentration remaining; the x-axis shows time. Curve A (pH 1) declines steeply; Curve B (pH 7) remains high throughout; Curve C (pH 13) declines steeply, similar to Curve A.
a
Identify which pH condition(s) produce the fastest hydrolysis of ethyl ethanoate and describe the trend shown by Curve B. [1]
b
Explain why both strongly acidic and strongly basic conditions accelerate ester hydrolysis compared to neutral conditions. [1]
c
Discuss the significance of ester stability at neutral pH for their use as food flavourings, referring to shelf life and flavour integrity. [1]
Solutions
3QuestionReaction:Alcohol + Carboxylic acid → Ester + WaterAssessment Practice
5 marks~8 minCriterion C
A student investigates the esterification of ethanol and ethanoic acid using a reflux apparatus with concentrated sulfuric acid as a catalyst. Equal amounts of each reactant (0.50 mol) are used.
Mass of water collected at 10-minute intervals:
The student hypothesises that "the reaction reaches completion after 30 minutes."
Mass of water collected at 10-minute intervals:
| Time (min) | 10 | 20 | 30 | 40 | 50 | 60 |
|---|---|---|---|---|---|---|
| Water (g) | 4.1 | 6.8 | 7.2 | 7.2 | 7.2 | 7.2 |
The student hypothesises that "the reaction reaches completion after 30 minutes."
a
Calculate the theoretical mass of water produced if the reaction goes to completion. [2]
b
Deduce whether the experimental data support the student's hypothesis. [1]
c
Evaluate the claim that the reaction reaches completion, using your knowledge of the nature of esterification reactions. [2]
Solutions
4QuestionStructure of estersAssessment Practice
6 marks~9 minCriterion B
A student reacted methanoic, ethanoic, propanoic, butanoic, and pentanoic acids separately with ethanol under identical conditions (same temperature, concentration, catalyst, and reaction time). Results are shown below.
| Carboxylic acid | methanoic | ethanoic | propanoic | butanoic | pentanoic |
|---|---|---|---|---|---|
| Carbon chain length | 1 | 2 | 3 | 4 | 5 |
| Yield (\%) | 92 | 85 | 78 | 72 | 67 |
a
Describe the pattern in percentage yield as carbon chain length increases. [2]
b
Deduce the percentage yield for the reaction of hexanoic acid with ethanol under the same conditions, using the pattern you identified. [2]
c
Explain, using collision theory, why percentage yield decreases as carbon chain length increases. [2]
Solutions
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