Question

To $100mL$ of an aqueous solution of $0.1MC{H}_{3}COOH$ $\left(K_a=2\times 10^{-5}\right),0.01mol$ of $HCl(g)$ is passed. Select correct options regarding the resulting solution.

• A. Degree of dissociation of acetic acid in resulting solution is $10^{-4}$
• B. $pH$ of resulting solution is nearly $1$
• C. Degree of dissociation of water in resulting solution is $1.8\times 10^{-15}$
• D. Concentration of $O{H}^{-}$ ions contributed by water in resulting solution is $10^{-7}M$

Answer 1

Answer: (C)

${}^{n}C{H}_{3}COOH=0.1\times 0.1=0.01mol$

${}^{n}HCl=0.01mol$

${\left[H^{+}\right]}_f=\frac{0.01}{0.1}=0.1M$

$pH=1$



$2\times 10^{-5}=\frac{X\times 0.1}{0.1}$

$x=2\times 10^{-5}$

$\alpha C{H}_{3}COOH=\frac{2\times 10^{-5}}{0.1}=2\times 10^{-4}$

$H_{2}O\rightleftharpoons H^{+}+O{H}^{-},10^{-14}=0.1\times \left[O{H}^{-}\right]$ $\left[O{H}^{-}\right]=10^{-13}M$

$\alpha \left(H_{2}O\right)=\frac{10^{-13}}{\frac{1000}{18}}$

$=18\times 10^{-16}=1.8\times 10^{-15}$