Law of Conservation of Mass Practice Problems

Shown in the figure below is a reaction mixture.

Determine from the following representations the product mixture that follows the law of conservation of mass.

Calculate the mass of PCl₃ is formed by the reaction of 13.54 g sample of phosphorus and 64.26 g of chlorine assuming it is the only product produced. 

In a balanced chemical equation, which of the following must have the same values on both sides?

I. the molecules of each type on each side
II. the atoms of each type on each side
III. the mass on each side

A small amount of octane (a volatile liquid and a component of gasoline) is put into a sealed container that has a spark system fitted into it. The container is filled with excess oxygen and then sealed. When the spark system is turned on, the liquid inside starts burning. Does burning change the mass of the contents inside the container?