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Esterification and naming esters — Free MYP5 Chemistry Practice Questions
1QuestionNaming esters: Alcohol part (alkyl) + acid part (oate)Concept Practice
2 marks~3 minCriterion A
The structural formulas of methanol () and butanoic acid () are shown below.
[Structural formula diagram]
[Structural formula diagram]
a
State the complete IUPAC name of the ester formed when methanol reacts with butanoic acid in a condensation reaction. [1]
b
Deduce which part of each reactant molecule contributes to the ester name, and explain the order in which those parts are combined to produce the IUPAC name. [1]
Solutions
2QuestionHydrolysis of esters (basic idea)Assessment Practice
2 marks~3 minCriterion C
Ethyl ethanoate () is an ester used as a solvent in nail-varnish remover. When ethyl ethanoate is warmed with water in the presence of a dilute acid catalyst, the ester linkage () breaks.
a
State the two organic products formed. [1]
b
Deduce which reactant provides the oxygen atom that becomes part of the carboxylic acid product, and explain how the position of the ester linkage in the structural formula supports your answer. [1]
Solutions
3QuestionHydrolysis of esters (basic idea)Assessment Practice
4 marks~6 minCriterion D
Aspirin (acetylsalicylic acid) undergoes hydrolysis in the stomach according to the equation:
The stomach maintains a pH of 1.5–3.5. Aspirin is used to relieve pain and reduce inflammation, but it is also associated with stomach irritation and ulcers.
The stomach maintains a pH of 1.5–3.5. Aspirin is used to relieve pain and reduce inflammation, but it is also associated with stomach irritation and ulcers.
a
Explain how the two products of aspirin hydrolysis account for both its therapeutic effect and the side effect of stomach irritation. [2]
b
A simplified model of this reaction assumes constant pH and ignores enzyme activity throughout the digestive tract. Evaluate one limitation of this model in predicting the actual behaviour of aspirin in the human body. [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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