Magnesium oxide is not very soluble in water

CHEMISTRY · Subjective · A Level · Chemistry · Acids and bases · Acids and bases

Problem

Magnesium oxide is not very soluble in water, so it is difficult to titrate directly. Its purity can be determined using a back-titration method.

4.08\,\text{g}

of impure magnesium oxide was completely dissolved in

100.0\,\text{cm}^3

2.00\,\text{mol dm}^{-3}

aqueous hydrochloric acid. The excess acid required

19.70\,\text{cm}^3

0.200\,\text{mol dm}^{-3}

aqueous sodium hydroxide for neutralization. Determine the percentage purity of the impure magnesium oxide.