1. 1
   A food scientist analyses a sample of vinegar and identifies its acidic component as ethanoic acid, CH3COOH. The scientist then tests the vinegar's reactions to confirm it behaves as a typical weak acid.

   (a)

   Which functional group is present in ethanoic acid?

   [1 mark]

   • A-COOH
   • B-OH
   • CC=C
   • D-NH2

   (b)

   The scientist compares ethanoic acid with hydrochloric acid of the same concentration and finds ethanoic acid has a higher pH. Which statement explains this observation?

   [1 mark]

   • AEthanoic acid does not contain any H+ ions in aqueous solution
   • BEthanoic acid is a strong acid, completely dissociating in aqueous solution
   • CHydrochloric acid is a weak acid, only partially dissociating in aqueous solution
   • DEthanoic acid is a weak acid, only partially dissociating in aqueous solution

   (c)

   The scientist adds a small piece of magnesium ribbon to a sample of the vinegar. Describe what would be observed and name the two products of this reaction.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A manufacturer of scented candles reacts ethanoic acid with ethanol, using an acid catalyst, to produce a fragrant compound for use in the candle wax.

   (a)

   Which class of compound is formed by this reaction?

   [1 mark]

   • AAlkene
   • BEster
   • CAlkane
   • DSalt

   (b)

   What is the name of the ester formed when ethanoic acid reacts with ethanol?

   [1 mark]

   • AMethyl ethanoate
   • BEthanoic ethanolate
   • CEthyl ethanoate
   • DEthyl methanoate

   (c)

   State the other product formed alongside the ester in this reaction, and state the role of the acid used in the reaction.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   In traditional vinegar-making, records describe wine being left to 'sour' naturally over weeks, and the resulting liquid being tested by its reaction with chalk (calcium carbonate) to confirm it was now acidic. Historians also note that the soured wine reacted much less vigorously with the chalk than a strong mineral acid of the same concentration would have.

   (a)

   Name the type of reaction between the soured wine and chalk, state the gas that would be produced, and describe a test to confirm the identity of this gas.

   [3 marks]

   (b)

   Explain, in terms of dissociation in aqueous solution, why the soured wine (containing ethanoic acid) reacted less vigorously with the chalk than a strong mineral acid, such as hydrochloric acid, of the same concentration would have.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A cosmetics company wants to manufacture a range of fragrant esters for perfumes, using various carboxylic acids and alcohols as starting materials.

   (a)

   Explain how carboxylic acids react with alcohols to form esters, and describe how the properties of the carboxylic acid used (its formula, functional group and behaviour as a weak acid) determine the identity of the ester produced.

   [6 marks]

   (b)

   Before scaling up production, the company's quality team wants to confirm the purity of their ethanoic acid stock and rules out any hydrochloric acid contamination. Explain how the reactions of ethanoic acid with metals, bases and carbonates could be used to confirm it is behaving as a typical weak acid, and discuss why simply observing a positive reaction with a metal would not, on its own, be enough to distinguish ethanoic acid from a strong acid such as hydrochloric acid.

   [6 marks]

   Total for question 4: 12 marks

End of questions