This question is about carboxylic acids.
Carboxylic acids belong to a homologous series.
Table 1 shows information about three carboxylic acids in this homologous series.
| Name | Formula | pH of a 0.01 mol/dm30.01\text{ mol/dm}^30.01 mol/dm3 solution |
|---|---|---|
| Ethanoic acid | CH3COOH\text{CH}_3\text{COOH}CH3COOH | 3.39 |
| Propanoic acid | (i) | 3.44 |
| (ii) | CH3CH2CH2COOH\text{CH}_3\text{CH}_2\text{CH}_2\text{COOH}CH3CH2CH2COOH | 3.48 |
Complete Table 1 by giving the chemical formula representing (i) and the name representing (ii).
Propanoic acid ionises in water.
The equation for the reaction is:
CH3CH2COOH(aq)⇌CH3CH2COO−(aq)+H+(aq)\text{CH}_3\text{CH}_2\text{COOH(aq)} \rightleftharpoons \text{CH}_3\text{CH}_2\text{COO}^-\text{(aq)} + \text{H}^+\text{(aq)}CH3CH2COOH(aq)⇌CH3CH2COO−(aq)+H+(aq)
Explain how the equation shows that propanoic acid is a weak acid.
A student adds a solution of propanoic acid to sodium carbonate in an open flask on a balance.
Explain what happens to the mass of the flask and its contents during the reaction.
The student compares the rates of reaction of sodium carbonate with:
The rate of the reaction with ethanoic acid is greater than the rate of the reaction with propanoic acid.
Explain why.
You should refer to ions in your answer and use information from Table 1.