2.1 definitions

Question 1

Relative isotopic mass

Answer 1

is the mass of an atom of an isotope compared with one twelfth of the mass of an atom of carbon-12.

Question 2

Relative atomic mass, Ar

Answer 2

is the weighted mean mass of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12.

Question 3

Amount of a substance

Answer 3

is the quantity that has moles as its unit. Chemists use ‘amount of substance’ as a way of counting atoms.

Question 4

A mole

Answer 4

is the amount of any substance containing as many particles as there are carbon atoms in exactly 12 g of the carbon-12 isotope.

Question 5

The Avogadro constant, NA

Answer 5

is the number of atoms per mole of the carbon-12 isotope (6.02 x 10 (to the power of) x 23 mol-1).

Question 6

Molar mass, M

Answer 6

is the mass per mole of a substance. The units of molar mass are g mol-1.

Question 7

Molar gas volume

Answer 7

is the volume per mole of a gas. The units of molar volume are dm3 mol-1. At room temperature and pressure, the molar volume is approximately 24.0 dm3 mol-1.

Question 8

The concentration

Answer 8

of a solution is the amount of solute, in mol, dissolved per 1 dm3 (1000cm3) of solution.

Question 9

A standard solution

Answer 9

is a solution of known concentration. Standard solutions are normally used in titrations to determine unknown information about another substance.

Question 10

Percentage (%) yield

Answer 10

(actual amount, in mol, of product / theoretical amount, in mol, of product) x 100

Question 11

Atom economy

Answer 11

Atom economy = (molecular mass of the desired product / sum of molecular masses of all products) x 100

Question 12

Hydrated

Answer 12

refers to a crystalline compound containing water molecules.

Question 13

Anhydrous

Answer 13

refers to a substance that contains no water molecules.

Question 14

Water of crystallisation

Answer 14

refers to water molecules that form an essential part of of the crystalline structure of a compound.