Can someone help me with this chemistry problem?

Question

I thought I knew how to do it, but I can't get the right answer...

Magnesium burns in air to produce magnesium oxide, MgO, and magnesium nitride, Mg3N2. Magnesium nitride reacts with water to give ammonia.


Mg3N2(s) + 6H2O(l) ==> 3Mg(OH)2(s) + 2NH3(g)


What volume (in L) of ammonia gas at 24oC and 743 mmHg will be produced from 4.37 g of magnesium nitride?

Answer 1

Notice that 1 mole of Mg3N2 will produce 2 moles of ammonia. Also molecular mass of Mg3N2 is 100.928 and of NH3 is 17.0306 g/Mol.
4.37g of Mg3N2
<==> 4.37/100.928 = 0.0433 (Mol) of Mg3N2
<==> Produce 0.0433 Mol *2 = 0.0866 Mol of NH3
<==> (from ideal gas law PV=nRT)
V = nRT/P = 0.0866*0.08206*297*(760/743) = 2.16 (L)
2.16 L of ammonia gas at 24oC and 743 mmHg will be produced from 4.37 g of magnesium nitride.