Waec Model Questions Vol1 2017 Chemistry Question 30

A student carries out the esterification of acetic acid with ethanol: CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O. (a) Starting with 0.050 mol CH₃COOH, 0.080 mol C₂H₅OH and excess H₂SO₄ as catalyst, the equilibrium mixture contains 0.030 mol of ethyl acetate. Calculate the equilibrium constant K_c for the reaction (assume the total volume is 1 L). (b) If instead 0.050 mol of each reactant are used and the reaction proceeds to 80 % completion (based on the limiting reagent), what mass of ethyl acetate is obtained? (c) The isolated ester (from part b) is then hydrolysed completely with exactly 0.050 mol of NaOH in 250 mL of water. Assuming the hydrolysis is quantitative and the solution contains only Na⁺, acetate ion and excess OH⁻, calculate the pH of the final solution. (Take K_a of acetic acid = 1.8×10⁻⁵.)