Question

The pH value of ${10}^{-7}$ M solution $HCl$ is:

• A. equal to 1
• B. equal to 2
• C. less than 7
• D. equal to 0

Answer 1

The correct option is C less than 7

$\left[H^{+}\right]$ from $HCl={10}^{-7}M$

$\left[H^{+}\right]$ from $H_{2}O={10}^{-7}M$

Total $\left[H^{+}\right]=2\times {10}^{-7}M$

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

$=-\log (2\times {10}^{-7})$

$=7-\log 2$

so the value is less than 7