Suppose you designed an experiment in which you burned a known quantity of magnesium in air. You used the product to determine how many moles of oxygen would react with the known number of moles of magnesium. Why would burning magnesium in air cause a source of error for this calculation?

Answer 1

2Mg + O2 ==> 2MgO
BUT air also contains N2 and at the elevated temperature of burning Mg it also combines with N2 as
3Mg + N2 ==> Mg3N2.
So when you weigh the MgO you actually are weighing mostly MgO but with some Mg3N2. Since O2 and N2 don't weigh the same and since O and N don't combine in the same ratio with Mg you have an error.

Answer 2

I actually have a question

Answer 3

I have a question how many miles of oxygen would it take to react with 1.0 moles of magnesium