Question

At ${90}^{\circ }\text{C}$, pure water has $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]={10}^{-6}\text{M}$, what is the value of $K_w$ at this temperature?

• A. ${10}^{-6}$
• B. ${10}^{-12}$
• C. ${10}^{-13}$
• D. ${10}^{-14}$

Answer 1

Answer: (B)

${10}^{-12}$

$K_w$ is temperature dependent, $\left[H_3{O}^{+}\right]$ = ${10}^{-6}M=\left[O{H}^{-}\right]$

$Kw=\left[H^{+}\right]\times \left[O{H}^{-}\right]={10}^{-6}\times {10}^{-6}={10}^{-12}$