Gce Model Questions Vol1 2023 Chemistry Question 30

Starting with 10.0 g of benzoic acid (\(\mathrm{C_7H_6O_2}\), M = 122.12 g mol⁻¹), a chemist carries out a two‑step synthesis of ethyl benzoate (\(\mathrm{C_9H_{10}O_2}\), M = 150.17 g mol⁻¹). In the first step, benzoic acid is converted to benzoyl chloride using thionyl chloride with an isolated yield of 85 %. In the second step, the benzoyl chloride reacts with excess ethanol in the presence of pyridine to give ethyl benzoate with a yield of 78 %. Excess reagents are used, and the reactions are 1:1 stoichiometric.\n\n(a) Calculate the theoretical mass of ethyl benzoate that could be obtained from 10.0 g of benzoic acid (assuming 100 % yield in both steps).\n(b) Calculate the actual mass of ethyl benzoate obtained after accounting for the yields of both steps.\n(c) Determine the overall percentage yield of the process.\n(d) If the crude product is purified by recrystallisation with a recovery of 90 %, what mass of pure ethyl benzoate is finally obtained?