| Date | May 2009 | Marks available | 2 | Reference code | 09M.3.hl.TZ2.D2 |
| Level | HL | Paper | 3 | Time zone | TZ2 |
| Command term | Write | Question number | D2 | Adapted from | N/A |
Question
Chemists can change structures of substances in order to produce chemicals with desired properties.
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.
Markscheme
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
Examiners report
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.
