20 mL of 0.1 M NH_4 OH is mixed with 40 mL of 0.05 M HCl. The pH of the mixture is nearest to: (Given: K_b ( NH_4 OH )=1 × 10^-5, log 2=0.30, log…

$\displaystyle 20$ mL of $\displaystyle 0.1 \mathrm{M} \mathrm{NH}_4 \mathrm{OH}$ is mixed with $\displaystyle 40$ mL of $\displaystyle 0.05$ M HCl . The pH of the mixture is nearest to : (Given : $\displaystyle \mathrm{K}_{\mathrm{b}}\left(\mathrm{NH}_4 \mathrm{OH}\right)=1 \times 10^{-5}, \log 2=0.30, \log 3=0.48, \log 5=0.69, \log 7=0.84, \log 11=$ $\displaystyle 1.04$)