The hydrolysis of acetic anhydride in excess water to form acetic acid, (CH₃CO)₂O + H₂O→2CH₃COOH, was studied by Elridge and Piret, who found that the rate at 15^◦C is first order in anhydride, with k = 0.0567 min⁻¹. A batch reactor initially holds 100 kg of anhydride. How long will it take for 90 kg to be converted to acid? 99 kg?