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The Mole and Avogadro's Constant



Amount of Substance

AQA Content

using the Avogadro constant
using mass of substance, Mr, and amount in moles
using concentration, volume and amount of substance in a solution.
Students will not be expected to recall the value of the Avogadro constant.

Specification Notes

The Avogadro constant as the number of particles in a mole.
The mole as applied to electrons, atoms, molecules, ions, formulas and equations.
The concentration of a substance in solution, measured in mol dm–3.


The mole is a unit of measurement used in chemistry to express amounts of substances.

Here are some key points for A Level Chemistry:
The mole is defined as the amount of a substance that contains the same number of particles (atoms, molecules, ions, or other entities) as there are in 12 grams of carbon-12.

The number of particles in a mole is known as Avogadro's number, which is approximately 6.02 x 10^23 particles per mole.

The mass of one mole of a substance is equal to its relative atomic or molecular mass in grams.

The mole can be used to convert between the mass, number of particles, and volume of a substance.

To calculate the number of moles of a substance, the mass of the substance is divided by its molar mass.

The molar mass of a substance can be calculated by adding up the atomic masses of its constituent atoms or the molecular masses of its constituent molecules.

The mole is commonly used in stoichiometry calculations, which involve balancing chemical equations and calculating the quantities of reactants and products involved in a chemical reaction.

A strong understanding of the mole concept is important in chemistry, It is a fundamental concept that underlies many topics, including chemical reactions, stoichiometry, and solution chemistry.


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