Reactive Formulae Mass & % Mass

Question 1

What is the law of conservation of mass? (1789)

Answer 1

The total mass of the products formed in a reaction is equal to the total mass of the reactants

Question 2

What is the formulae for the percentage of relative formulae mass?

Answer 2

Mass of the given substance in question
———————————————————- X 100
Total mass in the formulae

Question 3

What percentage of magnesium oxide is magnesium?

Answer 3

1 - write it (MgO)
2 - Relative atomic masses (Mg=24, O=16)
3 - Calculate (24/40 X 100 = 60%)

Ans = 60%