A student burned her magnesium sample according to the procedure and obtained a light gray product. Since the crucible looked dirty anyway, she skipped the steps to convert the Mg3N2 contamination to MgO, weighed the gray sample, and calculated the mass of her product. Was her resulting mass likely to be higher or lower the expected

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.