1 mole of a substance is 6.02 × 10²³ particles of it. The mass of a mole of a substance is its relative mass in grams.

Avogadro's constant is the number of particles in one mole of a substance (6.02 × 10²³ mol⁻¹).

The relative formula mass (RFM or Mᵣ) of a substance is the sum of the relative atomic masses of all the atoms in its formula.

Moles and masses

Combined science

Three types of chemical reaction

Conservation of mass

Balancing equations

The mole

Uncertainties in measurements: chemistry

Representations of a mole

Mass in a chemical reaction: using moles

Limiting reactants

Determining an equation from given values

Determining an equation experimentally: magnesium oxide

Determining an equation experimentally: sodium hydrogencarbonate

In the Making salts unit, pupils will learn about the production of pure salts, concentration and strength of acids, and what makes acids acidic and how bases can neutralise them.

In the Understanding Chemical Reactions unit, pupils learned about how atoms rearrange during chemical reactions and the conservation of mass.

This unit covers writing chemical formulae, balancing equations, and using the conservation of mass. It includes calculating moles, empirical formulae, relative formula masses, and theoretical yields. Emphasis is on stoichiometry, concentration, gas volumes, and using standard form.

Calculations involving masses

Physical activity and equipment requiring safe use

Which equation best matches this description of a chemical reaction?  "Four moles of aluminium atoms react with three moles of oxygen molecules to form two moles of aluminium oxide formula units".

moles = mass (g) × relative formula mass

mass (g) = moles ÷ relative formula mass

mass (g) = moles × relative formula mass

moles = mass (g) ÷ relative formula mass

Which of the following shows a correct mathematical relationship between moles, mass (g), and a substance's relative formula mass (RFM)?

The standard unit for mass in chemistry is {{}}.

Sort the following substances into order of increasing mass.

There are fewer nitric acid particles in 10 g

There are the same number of particles of nitrogen and nitric acid in 10 g

There are more nitric acid particles in 10 g

How does the number of particles in 10 g of nitric acid, HNO₃, compare to the number of particles in 10 g of nitrogen?

Match the mass (g) of the following substances to the correct number of moles.

Which of the following is the correct chemical formula for calcium carbonate?

describes a reaction, indicating the reactants and products

shows the number of atoms of each element in a substance

number placed in front of a chemical formula to balance an equation

written slightly below and to the side of another character

indicates the physical state of substances in a reaction

Match each keyword to the correct definition.

Which chemical equation is correctly balanced?

Match each element to its correct relative atomic mass.

The relative formula mass of sodium sulfide, Na₂S is {{}}. 

The relative formula mass of Al(OH)₃ is {{}}.

Starter Quiz