Question

At ${90}^{o}C$, pure water has $\left[H^{+}\right]={10}^{-6}M$. The value of $K_w$ at ${90}^{o}C$ is __________.

• A. ${10}^{-6}$
• B. ${10}^{-8}$
• C. ${10}^{-12}$
• D. ${10}^{-14}$

Answer 1

Answer: (C)

${10}^{-12}$

At ${90}^{o}C$, pure water has $\left[H^{+}\right]={10}^{-6}M$.

In pure water, $\left[H_3{O}^{+}\right]=\left[O{H}^{+}\right]$

The value of $K_w$ at ${90}^{o}C,$ $K_w=\left[H_3{O}^{+}\right]\left[O{H}^{-}\right]={10}^{-6}\times {10}^{-6}={10}^{-12}$