Question

When the reading of pH meter changes from $4$ to $6$. The hydrogen ion concentration in the solution

• A. is halved
• B. is doubled
• C. increases $100$ times
• D. decreases $100$ times

Answer 1

The correct option is D decreases $100$ times

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

$4=-log\left[H^{+}\right]$

$\left[H^{+}\right]={10}^{-4}$

$6=-log\left[H_{new}^{+}\right]$

$H_{new}^{+}={10}^{-6}$

$\frac{H_{new}^{+}}{H^{+}}=\frac{{10}^{-6}}{{10}^{-4}}$

$H_{new}^{+}={10}^{-2}{H}^{+}$

Hence, $H^{+}$ ion concentration decreases $100$ times.