A substance's empirical formula shows the simplest whole number ratio of atoms of each element in a compound.

To evaluate something is to make a judgement about it with respect to a particular purpose.

A mole of something is 6.02 × 10²³ of it. The mass of a mole of a substance is its relative mass expressed in grams.

Relative atomic mass is the mean mass of an atom relative to 1/12th the mass of an atom of carbon–12.

Deducing an empirical formula experimentally: using moles

Combined science

Three types of chemical reaction

Conservation of mass

Balancing equations

The mole

Moles and masses

Empirical formula calculations: using moles

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: 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

24 g of magnesium reacted with oxygen, producing 40 g of magnesium oxide.
Calculate the mass of oxygen that reacted. 

To allow oxygen to react with the magnesium.

To observe the magnesium's colour change.

Why is it important to periodically open the crucible during the heating of magnesium to produce magnesium oxide?

The combined mass of magnesium and oxygen that reacted is equal to the mass of magnesium oxide produced. 
This demonstrates the {{}} of mass, by accounting for all reactant and product masses.

Lifting the crucible lid too often, when heating magnesium to form magnesium oxide, can lead to which of the following experimental errors?

Given that 48 g of magnesium reacted with oxygen and produced 80 g of magnesium oxide, calculate the mass of oxygen that reacted and deduce the empirical formula of magnesium oxide.

In an experiment, 5.4 g of aluminium reacts with 4.8 g of oxygen to form aluminium oxide. 
What is the simplest whole number ratio of aluminium to oxygen (Al : O)?

The simplest whole number ratio of atoms in a compound.

What does an empirical formula represent?

Which empirical formula indicates a 1 : 1 ratio of metal to nonmetal ions?

The empirical formula demonstrates the simplest whole number ratio of elements, which aligns with the stoichiometric ratios in {{}} chemical equations.

helps calculate the molar ratio of elements.

The relative atomic mass of elements is crucial in determining the empirical formula because it ...

If 12 g of carbon react with 32 g of oxygen, what is the empirical formula of the resulting compound?

A compound contains 32.7% sulfur, 2.0% hydrogen, and 65.3% oxygen combine to form a compound. Determine the empirical formula.

Deducing an empirical formula experimentally: using moles

Lesson outcome

Content guidance