Determine the percentage experimental yield of the product after recrystallization. The molar masses are as follows: M(salicylic acid) = 138.13 g mol⁻¹, M(aspirin) = 180.17 g mol⁻¹. (You do not need to process the uncertainties in the calculation.)

Suggest why isolation of the crude product involved the addition of ice-cold water.

Justify the conclusion that recrystallization increased the purity of the product, by reference to two differences between the melting point data of the crude and recrystallized products.

State why aspirin is described as a mild analgesic with reference to its site of action.

ALTERNATIVE 1:
«theoretical yield = \(\frac{{1.552\,{\text{g}}}}{{138.13\,{\text{g}}\,{\text{mo}}{{\text{l}}^{ - 1}}}}\) × 180.17 g mol⁻¹ =» 2.024 «g»

«experimental yield = \(\frac{{1.124{\rm{g}}}}{{2.024{\rm{g}}}}\) × 100 =» 55.53 «%»

ALTERNATIVE 2:
«\(\frac{{1.552\,{\text{g}}}}{{138.13\,{\text{g}}\,{\text{mo}}{{\text{l}}^{ - 1}}}}\)»= 0.01124 «mol salicylic acid/aspirin theoretical» AND

«\(\frac{{1.124\,{\text{g}}}}{{180.17\,{\text{g}}\,{\text{mo}}{{\text{l}}^{ - 1}}}}\)»= 0.006239 «mol aspirin experimental»

«experimental yield = \(\frac{{0.006239{\rm{mol}}}}{{0.01124{\rm{mol}}}}\) x 100 =» 55.51 «%»

Accept answers in the range 55.4 % to 55.7 %.
Award [2] for correct final answer.

low temperature gives greater difference between solubility of aspirin and impurities
OR
«product» crystallizes out from cold solution/«ice-cold water/lower temperature» speeds up crystallization process
OR
aspirin/product has low solubility «in water» at low temperatures

intercepts pain stimulus at source/acts at site of pain
OR
interferes with production of pain sensitizing substances/prostaglandins «at site of pain»

recrystallized melting point is higher
OR
recrystallized melting point is closer to pure substance/literature value

smaller range of values