IB Chemistry home > Syllabus 2016 > Stoichiometry > Gases

Syllabus ref: 1.3

This section covers the behaviour of pure and mixtures of ideal gases. Chemical reactions involving gases are required.

Nature of science:

Making careful observations and obtaining evidence for scientific theories. Avogadro's initial hypothesis.


Reactants can be either limiting or excess.

Avogadro's law enables the mole ratio of reacting gases to be determined from volumes of the gases.

The molar volume of an ideal gas is a constant at specified temperature and pressure.

Applications and skills

Calculation of reacting volumes of gases using Avogadro's law.

Solution of problems and analysis of graphs involving the relationship between temperature, pressure and volume for a fixed mass of an ideal gas.

Solution of problems relating to the ideal gas equation.

Explanation of the deviation of real gases from ideal behaviour at low temperature and high pressure.

Obtaining and using experimental values to calculate the molar mass of a gas from the ideal gas equation.

In Chapter 3.4