A sample of Mg was burnt in air to give a mixture of MgO and $Mg_3N_2$.The ash was dissolved in 60meq. of HCl and the resulting solution was back titrated with NaOH.12meq of NaOH were required to reach the end point.An excess of NaOH was added and the solution distilled.The ammonia released was then trapped in 10Meq of second acid solution .Back titration of this solution required 6Meq of the base.Calculate the percentage of Mg burnt to the nitride.
