Question

Magnesium combines with oxygen to form magnesium oxide. If 10.57 g of

magnesium reacts completely with 6.96 g of oxygen, what is the percent by mass of
oxygen and magnesium?

Answer 1

The total mass is 10.57+6.96=17.53 g.

So, the percent by mass of magnesium is (10.57)/(17.53) * 100 = 60.3%

The percent by mass of oxygen is (6.96)/(17.53) * 100 = 39.7%