Water of Crystallisation

Question 1

Water of crystallisation is when

Answer 1

some compounds can form crystals which have water as part of their structure

Question 2

A compound that contains water of crystallisation is called a

Answer 2

hydrated compound

Question 3

The water of crystallisation is separated from the main formula by a

Answer 3

by a dot when writing the chemical formula of hydrated compounds
E.g. hydrated copper(II) sulfate is CuSO4∙5H2O

Question 4

A compound which doesn’t contain water of crystallisation is called an

Answer 4

anhydrous compound
E.g. anhydrous copper(II) sulfate is CuSO4

Question 5

A compound can be hydrated to different degrees
E.g.

Answer 5

cobalt(II) chloride can be hydrated by six or two water molecules
CoCl2 ∙6H2O or CoCl2 ∙2H2O

Question 6

The conversion of anhydrous compounds to hydrated compounds is reversible by

Answer 6

heating the salt

Question 7

The degree of hydration can be calculated from experimental results:

Answer 7

he mass of the hydrated salt must be measured before heating

The salt is then heated until it reaches a constant mass

The two mass values can be used to calculate the number of moles of water in the hydrated salt - known as the water of crystallisation

REMEMBER WATER LEAVES NOT EVAPORATES AS IS SOLID

Question 8

PRACTICE