Question 7

7.1 Ethanoic acid (CH₃COOH) is an ingredient of household vinegar

7.1.1 Is ethanoic acid a WEAK acid or a STRONG acid? Give a reason for
the answer. (2)

7.1.2 An ethanoic acid solution has a pH of 3,85 at 25 °C. Calculate the
concentration of the hydronium ions, H₃O⁺(aq), in the solution. (3)

Sodium ethanoate, CH₃COONa(aq), forms when ethanoic acid reacts with sodium hydroxide.

7.1.3 Will the pH of a sodium ethanoate solution be GREATER THAN 7,
LESS THAN 7 or EQUAL TO 7? (1)

7.1.4 Explain the answer to QUESTION 7.1.3 with the aid of a balanced
chemical equation. (3)

7.2 Household vinegar contains 4,52% ethanoic acid, CH3COOH by volume

A 1,2 g impure sample of calcium carbonate (CaCO₃) is added to 25 cm³
household vinegar

On completion of the reaction, the EXCESS ethanoic acid in the household vinegar is neutralised by 14,5 cm³ of a sodium hydroxide solution of concentration 1 mol∙dm^-3. The balanced equation for the reaction is:

7.2.1 Calculate the number of moles of the unreacted ethanoic acid. (3)

7.2.2 Calcium carbonate reacts with ethanoic acid according to the
following balanced equation:

Calculate the percentage calcium carbonate in the impure sample if 1 cm ³
of household vinegar has a mass of 1 g. (8)

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