3.1.2 Amount of Substance

What is the definition for ‘Relative Atomic Mass (Ar)’?

Average mass of an atom of an element on a scale where an atom of carbon-12 is exactly 12.

What is the definition for ‘Relative Molecular mass (Mr)’?

Average mass of a molecule on a scale where an atom of carbon-12 is exactly 12.

What does ‘anhydrous’ mean?

Without water.

What does ‘hydrated’ mean?

With water

What does ‘water of crystallisation’ mean?

Water that is chemically bonded to a salt.

What is Avogadro’s constant?

6.022 × 10²³ mol^-1

Why might you not get the expected amount of a product? (1)

Reaction may be reversible.

Why might you not get the expected amount of a product? (2)

Some of the product may be lost when it is separated from the reaction mixture.

Why might you not get the expected amount of a product? (3)

Some of the reactants may react in other reactions.

What is ‘atom economy’?

A measure of what proportion of the products of a reaction are the desired product and how much is waste.

What is the ‘empirical formula’?

The simplest ratio of atoms of each element in a substance.

What is the ‘molecular formula’?

The exact amount of atoms of each element in a substance.