Which of the following expressions precisely denotes the dissociation constant ( or ) of pure water — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

The dissociation constant of water is defined as $K_d = \frac{[H^+][OH^-]}{[H_2O]}$. At $25^\circ C$, the ionic product $[H^+][OH^-] = K_w = 10^{-14}$. The molarity of pure water is $\frac{1000 \text{ g/L}}{18 \text{ g/mol}} = 55.5 \text{ M}$. Therefore, $K_d = \frac{10^{-14}}{55.5} = 10^{-14} \times (55.5)^{-1}$.