Q$1.$ A$.$ A liter of a solution containing $(0\mathrm{.}5M)$ of ammonia and $(0\mathrm{.}1)M$ of ammoninm chloride to which $0\mathrm{.}1$ mol of magnesium nitrate has been added. Calculate the percentage $(M{g}^{+2})$ needed to obtain a saturated solution of magnesium hydroxid $.$