Molar mass of KOH = 56.0 $\mathrm{g\,mol^{-1}}$ ∴ No. of moles of KOH = $\frac{0.561\ \mathrm{g}}{56.0\ \mathrm{g\,mol^{-1}}}$ = 0.01 mol and conc. of KOH = $\frac{0.01}{0.2\ \mathrm{L}}$ mol = 0.05 mol/L $\mathrm{KOH}_{\mathrm{(aq)}}$ → $\mathrm{K^{+}}_{\mathrm{(aq)}} + \mathrm{OH^{-}}_{\mathrm{(aq)}}$ $[\mathrm{K^{+}}]$ = $[\mathrm{OH^{-}}]$ = 0.05 M and $[\mathrm{H^{+}}]$ = $\frac{K_{w}}{[\mathrm{OH^{-}}]}$ = $\frac{1.0 \times 10^{-14}}{0.05}$ = 2.0 × $10^{-13}$ ∴ pH = - log (2.0 × $10^{-13}$) = 12.70