Chemistry - Ionic Equilibrium Question with Solution | TestHub

$KOH$ is a strong base and $HCOOH$ is a weak acid. The reaction produces $HCOOK$, a weak base.

Moles of $KOH=0.04L\times 0.2M=0.008$ moles

Moles of $HCOOH=0.16L\times 0.1M=0.016$ moles

After reaction, $0.016-0.008=0.008$ moles of $HCOOH$ remain and $0.008$ moles of $HCOOK$ are formed. This is a buffer solution.

$[H^{+}]=K_a\times \frac{[Acid]}{[Salt]}=2\times 10^{-4}\times \frac{0.008}{0.008}=2\times 10^{-4}$

$pH=-log(2\times 10^{-4})=4-log(2)=4-0.3=3.7$

$pOH=14-3.7=10.3$