Question

For each of the following choices A, B, C, find the one which describe as weaker acid:
(A) $K_a=X,K_a=3X$
(B) $\left[H^{+}\right]=X;\left[H^{+}\right]=3X$
(C) $pH=X,pH=3X$

Answer 1

$K_a$ of a stronger acid is greater than that of a weak acid.

$\left(A\right)$ ${K_a}_1=X,{K_a}_2=3X$

$\because {K_a}_2>{K_a}_1$

Acid $2$ is a stronger acid than Acid $1$.

$\left(B\right)$ $[H^{+}{]}_1=X,[H^{+}{]}_2=3X$

Since, $H^{+}$ furnished by acid $2$ ia more than acid $1$.

Acid $2$ is stronger than acid $1$.

$\left(C\right)$ $p{H}_1=X,p{H}_2=3X$

$\therefore [H^{+}{]}_1={10}^{-X}$ and $[H^{+}{]}_2={10}^{-3X}$

$\because {10}^{-X}>{10}^{-3X}$

$\therefore H^{+}$ furnished by acid $1$ is more than acid $2$.

$\therefore$ Acid $1$ is stronger than acid $2$.