Question

If for a weak acid $HA,K_a=10^{-5}$ then value of $p{K}_b$ for $A_{(aq)}^{-}$ is

• A. 5
• B. 7
• C. 9
• D. 11

Answer 1

Answer: (C)

For conjugate acid-base pair.
$p{K}_b=14-p{K}_a$
$\left[p{K}_a=-\log K_a=-\log 10^{-5}=5\right]$
$=14-5=9$