EL6

Question 1

relative atomic mass Ar

Answer 1

mass of the atom of an element relative to carbon-12 (which has an Ar of exactly 12)

Question 2

relative formula/molecular mass Mr

Answer 2

sum of the Ar of the elements making up a compound

Question 3

a mole

Answer 3

relative atomic mass of a substance in grams

Question 4

formula unit

Answer 4

the formulae of a substance
eg. copper is Cu, oxygen is O2
in most covalent molecules the formula unit is the molecule

Question 5

Avogadro’s constant

Answer 5

number of formula units in one mole of a substance is a constant (6.02x10^23)

Question 6

molecular formula

Answer 6

the actual ratio (number) of atoms of each different element in a compound

Question 7

empirical formula

Answer 7

formula showing the simplest ratio of the numbers of atoms of each different element in a compound

Question 8

water of crystallisation

Answer 8

crystals of some ionic lattices include molecules of water which fit within the lattice in a regular manner
crystals are said to be hydrate
when hydrated crystals are heated, water of crystallisation is removed as steam to leave anhydrous solid