1 mole is 6×10²³ particles. Stoichiometry means the mole ratio of substances in a reaction.

no of moles = no of particles ÷ 6×10²³

The mass of a molecule compared to 1/12th of a carbon-12 atom.

M_r of A_nB_m = (n × A_r of A) + (m × A_r of B)

The mass of 1 mol of a substance, numerically equal to the A_r or M_r.

molar mass = mass in g ÷ no of moles

The percentage by mass of a compound that is made up of an element.

% mass of A in A_nB_m= nA_r ÷ M_r × 100%

The simplest ratio of atoms of each element in a compound.

1. Write the masses of each element
2. Divide by A_r
3. Divide by smallest number

Shows the number of atoms of each element in one simple molecule.

1. Find n = M_r ÷ mass of empirical formula
2. Multiply numbers in empirical formula by n

A mole of gas occupies 24 dm³ of volume at room temperature and pressure (rtp).

no of moles = gas volume in dm³ ÷ 24

The number of moles or mass of solutes per dm³ of solvent.

concentration = no of moles ÷ volume in dm³
concentration = mass ÷ volume in dm³

Carefully adding exact amount of one solution to completely react with another.

1. Find no of moles of titrant = concentration × volume
2. Use mole ratio to find no of moles of unknown
3. Find conc of unknown = no of mol ÷ volume

The reactant that is completely used up, limiting the amount of product.

1. Find the no of moles of reactants A and B provided
2. Find the no of moles of B needed if A were used up
3. A is limiting if there is less B needed than provided

The extent and efficiency of converting reactants to products.

% yield = expected yield ÷ theoretical yield × 100%

The percentage by mass of an impure mixture that comprises the pure substance.

% purity = mass of pure substance ÷ mass of impure mixture × 100%