Question

Which of the following expressions is not true?

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

Answer 1

Answer: (D)

$\left[H^{+}\right]=\left[{OH}^{-}\right]={10}^{-7}M$ for a neutral solution at all temperatures

For a neutral solution at ${25}^{0}C$ $pH$ and $pOH$ are both equal to 7 so $\left[H^{+}\right]=\left[O{H}^{-}\right]=\sqrt{K_w}$.

For an acidic solution $pH<7$ so $\left[H^{+}\right]>\sqrt{K_w}$. and $\left[O{H}^{-}\right]<\sqrt{K_w}$.As the temperature increases dissociation will increase so $pH$ of neutral solution will decrease.So $\left[H^{+}\right]$ is not equal to $\left[O{H}^{-}\right]$ or$\sqrt{K_w}$ at all temperatures.