Question

Which of the following expressions is/are not true?

• A. $\left[H^{+}\right]=\left[O{H}^{-}\right]=\sqrt{K_w}$ for a neutral solution at all temperatures
• B. $\left[H^{+}\right]>\sqrt{K_w}\&\left[O{H}^{-}\right]<\sqrt{K_w}$ for an acidic solution
• C. $\left[H^{+}\right]<\sqrt{K_w}\&\left[O{H}^{-}\right]>\sqrt{K_w}$ for an alkaline solution
• D. $\left[H^{+}\right]=\left[O{H}^{-}\right]={10}^{-7}M$ for a neutral solution at all temperatures

Answer 1

The correct option is D $\left[H^{+}\right]=\left[O{H}^{-}\right]={10}^{-7}M$ for a neutral solution at all temperatures

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

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

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

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

So

$\left[H^{+}\right]=\left[O{H}^{-}\right]=\sqrt{K_w}$ for a neutral solution at all temperatures

$\left[H^{+}\right]>\sqrt{K_w}\&\left[O{H}^{-}\right]<\sqrt{K_w}$ for an acidic solution

$\left[H^{+}\right]<\sqrt{K_w}\&\left[O{H}^{-}\right]>\sqrt{K_w}$ for an alkaline solution

$\left[H^{+}\right]=\left[O{H}^{-}\right]={10}^{-7}M$ for a neutral solution at ${25}^{o}C$ only. After that as we increase temp. more no of water molecules dissociate and conc. of both ions increases.