Question

The hydronium ion concentration in pure water is $1\, \times \,10^{-7}$ $mol\, L^{-1}$. The degree of dissociation of water is

• A. $1.8 \times 10^{-9}$
• B. $0.8 \times 10^{-8}$
• C. $9.8 \times 10^{-6}$
• D. $3 \times 10^{-9}$

Answer 1

Answer: (A)

If $\alpha$ is degree of dissociation
$H_{2}O \rightleftharpoons H^{+}+OH^{-}$
Initial conc. $C\,mol\,L^{-1}$
Equi. cone. : $C(1-\alpha) C \alpha\,C \alpha$
$[H^{+}]=C \alpha$ or $\alpha=\frac{\left[H\right]^{+}}{C}=\frac{1\times10^{-7}}{55.5}$
$=1.8 \times 10^{-9}$