-- Matter is neither created nor destroyed in a chemical reaction. Thus, the mass of the products of a chemical reaction must be equal to the mass of the starting materials. Formally, this concept is called the law of conservation of mass.
-- A sample of sodium reacts completely with 0.213 of chlorine, forming 351 of sodium chloride. What mass of sodium reacted?
-- When carbon is burned in air, it reacts with oxygen to form carbon dioxide. When 24.0 of carbon were burned in the presence of 75.4 of oxygen, 11.4 of oxygen remained unreacted. What mass of carbon dioxide was produced?