Aspirin is virtually insoluble in water. Use Table 20 in the Data Booklet to explain how aspirin can be made more water-soluble. Write an equation for the reaction.

react aspirin with sodium hydroxide/${\text{O}}{{\text{H}}^ - }$ to produce the (ionic) salt;

No M1 for reaction with CaCO₃ (as calcium salicylate is not water soluble).

${{\text{C}}_{\text{6}}}{{\text{H}}_{\text{4}}}{\text{(OCOC}}{{\text{H}}_{\text{3}}}{\text{)COOH}} + {\text{NaOH}} \to {{\text{C}}_{\text{6}}}{{\text{H}}_{\text{4}}}{\text{(OCOC}}{{\text{H}}_{\text{3}}}{\text{)COONa}} + {{\text{H}}_{\text{2}}}{\text{O}}$;

Accept ionic equation.

ECF for M2

Few candidates knew how to make aspirin more water-soluble – most answers showed a lack of understanding of the chemistry involved, namely reaction with NaOH to produce the ionic salt of aspirin.