C3 - Conservation Of Mass

What is the law of conservation of mass?

No atoms are lost or made during a chemical reaction, so the mass of products equals the mass of reactants.

What does "reactants" mean in a chemical reaction?

The starting substances in a reaction.

What does "products" mean in a chemical reaction?

The new substances formed in a reaction.

If 24 g of magnesium reacts with 71 g of chlorine, what mass of magnesium chloride is formed?

95 g (because mass of reactants = mass of products).

If 92 g of sodium reacts with 32 g of oxygen, what mass of sodium oxide is formed?

124 g (92 + 32).

If a reaction produces 112 g of calcium oxide and 88 g of carbon dioxide, what was the mass of calcium carbonate that reacted?

200 g (112 + 88).

If magnesium oxide reacts with 73 g of hydrogen chloride to make 95 g of magnesium chloride and 18 g of water, what mass of magnesium oxide reacted?

40 g (113 − 73).

How do you calculate the mass of products in a reaction?

Add the total mass of the reactants.

How do you calculate the mass of a missing reactant?

Total mass of products − mass of the other reactant(s).

Why is mass conserved in chemical reactions?

Because atoms are rearranged, not lost or created.