The initial rate of hydrolysis of methyl acetate ( 1 M ) by a weak acid (HA, 1 M ) is $1 / 100^{ ex

Question

The initial rate of hydrolysis of methyl acetate ( 1 M ) by a weak acid (HA, 1 M ) is $1 / 100^{	ext {th }}$ of that of a strong acid ( $\mathrm{HX}, 1 \mathrm{M}$ ), at $25^{\circ} \mathrm{C}$. The $K_{a}$ of HA is\

Professor PC Thomas Classes · Answer

(a) : Rate with respect to weak acid $$ R_{1}=k\left[\mathrm{H}^{+}ight]_{	ext {weak acid }} $$ and rate with respect to strong acid $$ \begin{array}{ll} & R_{2}=k\left[\mathrm{H}^{+}ight]_{	ext {strong acid }} \ 	herefore & \frac{R_{1}}{R_{2}}=\frac{k\left[\mathrm{H}^{+}ight]_{	ext {weak acid }}}{k\left[\mathrm{H}^{+}ight]_{	ext {strong acid }}}=\frac{1}{100} \ 	herefore \quad & {\left[\mathrm{H}^{+}ight]_{	ext {weak acid }}=\frac{1}{100}=0.01 \mathrm{M}} \ & \underset{1-0.01 \approx 1}{\mathrm{H} A} ightleftharpoons \mathrm{H}^{+}+A^{-} \ K_{a}=\frac{\left[\mathrm{H}^{+}ight]\left[\mathrm{A}^{-}ight]}{[\mathrm{HA}]}=\frac{0.01}{0.01 	imes 0.01} \ 1 \end{array}=1 	imes 10^{-4} . $$