Question

A 2.000 g sample of magnesium was burned in air to form an oxide.

After the product was purified it was found to have a mass of 3.317 g. What is the empirical formula for the product?

Answer 1

This is how I tried to answer...

1 mol of Mg= 24.3g
1 mol of O= 16.0 g

2.0 g Mg = 0.0823 mol Mag
1.317 g O (3.317-2.0) = 0.0823 mol O

empirical formula is MgO

Answer 2

Looks OK to me. Just to be picky watch what you are doing with the units and balancing equations, for example

2.0 g Mg = 0.0823 mol Mg

does not balance in terms of number or units.

Similarly

1.317 g O (3.317-2.0) = 0.0823 mol O

does not balance in terms of number or units.

Better as

Number of moles of magnesium is
2.0 g / 24.3 g mol^-1= 0.0823 mol

and number of moles of oxygen is

1.317 g /16 g mol^-1 = 0.0823 mol