d
\(4 \mathrm{gm}\) of \(\mathrm{NaOH}\) in \(100 \mathrm{L}\) sol. \(\Rightarrow 10^{-3} \mathrm{M}\) sol.

\(9.8 \mathrm{gm}\) of \(\mathrm{H}_{2} \mathrm{SO}_{4}\) in \(100 \mathrm{L}\) sol. \(\Rightarrow 10^{-3} \mathrm{M}\) sol.

Mixture : \(40 L\) of \(10^{-3} \mathrm{M} \mathrm{NaOH}\) and \(10 \mathrm{L}\) of

\(10^{-3} \mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}\) sol.

Final Conc. of \(OH^-=\frac{10^{-3}(40 \times 1-10 \times 1 \times 2)}{40+10}=6 \times 10^{-4} \mathrm{M}\)

\(\mathrm{pOH}=-\log \left(6 \times 10^{-4}\right)\)

\(=4-\log 6=4-0.60=3.40\)

\(\mathrm{pH}=14-3.40=10.60\)