\({K_{sp}} = [M{g^{ + 2 }}]{[O{H^ - }]^2}\)
\(1.0 \times {10^{ - 11}} = {10^{ - 3}} \times {[O{H^ - }]^2}\)
\([O{H^ - }] = \sqrt {\frac{{{{10}^{ - 11}}}}{{{{10}^{ - 3}}}}} = {10^{ - 4}}\)
\(\therefore \,pOH = 4\)
\(\therefore pH + pOH = 14\)
\(\therefore \,pH = 10\)