\begin{array}{*{20}c} {K_w = \left[ {OH^ - } \right]\left[ {H^ + } \right] = K_a \times K_b } \\ {\begin{array}{*{20}c} { = 1.0 \times 10^{ - 14} } & {at} & {25^\circ C} \\ \end{array}} \\ \end{array}

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