Balancing equations: a chemical equation is balanced when there are equal number of atoms and charges on both sides of the equation
- (s) = solid
- (l) = liquid
- (g) = gas
- (aq) = aqueous solution
- Relative atomic mass (Ar) is the average mass of naturally occurring atoms of an element on a scale where the C-12 atom has a mass of exactly 12 units.
- Relative molecular mass (Mr) is the sum of the relative atomic masses.
2) The Mole Concept
- A mole of a substance is the amount that contains the same number of units as the number of carbon atoms in 12 grams of carbon-12.
- A mole is the Ar or Mr expressed in grams e.g. 1 mole of Carbon-12 is equal to 12 grams.
- It is equal to
- this number is called Avogadro’s constant.
Number of Moles:
Moles in Gases:
- Moles per dm3
- 1mol/dm3 = 1M
- Grams per dm3, g/dm3
* 3) Calculate Empirical Formulae
* 4) Calculate Percentage Yield and Percentage Purity