Question

For a given solution $pH=6.9$ at ${60}^{0}C$ where $K_w={10}^{-12}$. The solution is:

• A. acidic
• B. basic
• C. neutral
• D. unpredictable

Answer 1

The correct option is B basic

$K_w=\left[H^{+}\right]\left[O{H}^{-}\right]$

For neutral solution, $\left[H^{+}\right]=\left[O{H}^{-}\right]$

Given, $K_w={10}^{-12}$

So, $\left[H^{+}\right]={10}^{-6}$

$pH=-log\left[H^{+}\right]=-log\left[{10}^{-6}\right]=6$

So, in such case, pH of neutral solution is 6. Therefore, a solution having pH 6.9 is basic.