Question

The pH of solution is 5.0 . To this solution , sufficient acid is added to decrease the pH to 2.0. The increase in hydrogen ion concentration is:

• A. 100 times
• B. 1000 times
• C. 2.5 times
• D. 10 times

Answer 1

The correct option is B 1000 times

Case-1 $pH=5\Rightarrow -lo{g}_{10}\left[H^{+}\right]=5\left[H^{+}\right]={10}^{-5}.....\left(1\right)$Case-2
$-lo{g}_{10}\left[H^{+}\right]=2$
$\left[H^{+}\right]={10}^{-2}.....\left(2\right)$
divide equation 1 by 2 we get
$\frac{{10}^{-2}}{{10}^{-5}}=1000times$
hence, the increase in hydrogen ion concentration is 1000 times.