1.1: The Mole Concept & Amount of Substance

What is the mole?

The mole is the amount of substance that contains exactly 6.02 × 10²³ elementary entities (Avogadro’s number).

What is Avogadro’s number?

6.02 × 10²³ mol⁻¹, the number of particles in one mole of a substance.

What is meant by “amount of substance”?

The quantity of a substance measured in moles (mol).

What is molar mass?

The mass of one mole of a substance, expressed in g mol⁻¹.

How do you calculate moles from mass?

n = mass divided by Mr

What is relative atomic mass (Ar)?

The weighted average mass of an atom of an element relative to 1/12 of a carbon-12 atom.

What is relative molecular mass (Mr)?

The sum of the relative atomic masses of all atoms in a molecule.

How do you calculate number of particles from moles?

N=n×NA​

NA = 6.02 × 10²³

What types of particles can be counted using moles?

Atoms, molecules, ions, electrons, or formula units.

Why is the mole concept important in chemistry?

It allows chemists to count particles by weighing substances, linking the microscopic and macroscopic scales.

What is the relationship between mass and number of particles?

Mass → moles → number of particles (via Avogadro’s number).

What is a common mistake when calculating molar mass?

Forgetting to include all atoms in the formula (especially in brackets).

What is a common unit mistake in mole calculations?

Not converting mass into grams before using the formula.