# The $pH$ of a solution is 5.00. To this solution, sufficient acid is added to lower the $pH$ to 2.00. The corresponding increase in $H_3O^+$ ion concentration is

(a) 1000 times

(b) 2.5 times

(c) 100 times

(d) 5 times

$[H_3O^+] = 10^{-5}$ M
On adding acid new $[H_3O^+] = 10^{-2}$
$\therefore$ Increase in $[H_3O^+] = 10^3$