Magnesium combines with oxygen to form magnesium oxide. If 24.46 g of magnesium reacts completely with 5.41 g of oxygen, what is the percent by mass of oxygen in magnesium oxide?
The magnesium oxide is MgO. The mass percent of oxygen is 16/(24.3+16)=39.7%. For the given reaction, in my opinion, there will be magnesium left after reaction.
