Answer:
The resulting mass will be higher than expected
Explanation:
We have to keep this in mind; When magnesium is being burnt in air, two reactions are taking place. The first one is;
2Mg(s) + O2(g) ------> MgO(s) -------1
And
3Mg(s) + N2(g) -------> Mg3N2(s) ---------2
Now, if the steps that should be taken to convert Mg3N2 to MgO are not taken, the reaction is much quicker but a higher mass of solid is obtained than what was expected.
This higher mass of solid obtained owes to the fact that Mg3N2 from reaction 2 was not converted to MgO leading to contamination of the product.