13. The table gives some information about the first five members of the carboxylic acid homologous series.

(a) (1) Estimate the boiling point of pentanoic acid. [1]

(ii) Draw the structure of butanoic acid. Show all atoms and bonds. [1]
(iii) Ethanoic acid reacts with sodium. Write an equation for this reaction. [1]

(b) Carboxylic acids react with alcohols to form esters.
(i) Name the ester formed when ethanoic acid reacts with ethanol. [1]
(ii) The diagram shows the repeat unit of poly(ethenyl ethanoate) Draw the structure of the monomer used to make poly(ethenyl ethanoate). [1]
(i) Calculate the empirical formula of X. [2]

(c) Carboxylic acid X contains 55.8% carbon, 7.0% hydrogen and 37.2% oxygen.
(ii) A molecule of carboxylic acid X contains four carbon atoms. What is its molecular formula? [1]
(iii) Carboxylic acid X is an unsaturated compound.
Give a test for an unsaturated compound. Include in your answer the test and the expected observation. [2]

carboxylic acid formula boiling point/"C methanoic acid 101 ethanoic acid CH, CO H 118 propanoic acid CHICOH 141 butanoic acid 166 pentanoic acid