Quantitative Chemistry - Conservation of Mass

What does the ‘Conservation Of Mass’ mean?

The Conservation of Mass states that no atoms are lost or made during a chemical reaction so the mass of products equals the mass of reactants.

Why do equations always need to be balanced?

Equations must be balanced to match the Conservation of Mass, so the number of atoms and type of atoms must be the same on both sides of the equation.

What is a precipitation reaction?

A precipitation reaction is one where two solutions react to form an insoluble solid called a precipitate.

What happens if a precipitation reaction takes place in a closed system? Why?

The total mass remains constant, as no matter can enter or leave the system.

Example of precipitate reaction: Calcium Chloride + Calcium Sulphate reacts to make…

Calcium Sulfate precipitate in Sodium Chloride solution (no change in mass)

What happens if the reaction takes place in an open system? What if it included a gas in the reaction?

The total mass may change, as matter can enter or leave the system. If a gas is present in the reaction with an open system, it may be allowed to escape and the total mass of the reaction will change as product mass is lost

What happens if you leave a reaction flask unclosed?

Mass will be lost from the reaction gas, or in case of an increase it may be due to one of the reactance being a gas found in the air and all products are either solids or liquids

What changes in the matter during a reaction?

The chemical and physical properties of the reactants as they transform into products