Question
A sample of magnesium was burnt in air to give a mixture of MgO and Mg3N2. The ash was dissolved in 60 meq. of HCl and the resultant solution was back-titrated with NaOH. 12 meq. of NaOH was required to reach the end point. An excess of NaOH was then added and the solution was distilled. The ammonia was then trapped in 10 meq. of a second acid solution. Back-titration of this solution required 6 meq. of the base. The percentage of magnesium burnt will be (as nearest integer) :