Acid catalysed hydrolysis of ester is first-order reaction and rate constant is given by

$k=\frac{2.303}{t}\log \frac{{\mathrm{V}}_{\mathrm{\infty }}-{\mathrm{V}}_0}{{\mathrm{V}}_{\mathrm{\infty }}-{\mathrm{V}}_t}$

where ${\mathrm{V}}_0,{\mathrm{V}}_t\text{ and }{\mathrm{V}}_{\mathrm{\infty }}$ are the volume of standard $\mathrm{NaOH}$ required to neutralized acid present at a given time; if ester is $50\%$ hydrolysed then :