Paper 1 - Reversible Reactions and Equilibria

Question 1

What can some reactions do and how is this indicated?

Answer 1

Some reactions are reversible
- This is indicated by the symbol ⇌ in
equations

Question 2

Describe the reversible reaction of the dehydration of hydrated copper(II) sulfate

Answer 2

• When Cu(II) Sulfate is bound to water, it forms blue crystals
• Heat the blue hydrated Cu(II) Sulfate to evaporate the water
• This leaves white anhydrous Cu(II) Sulfate powder
• Add 3 drops of water to the white powder to form the blue crystals

Question 3

Describe the reversible reaction of the effect of heat on ammonium chloride

Answer 3

• The thermal decomposition of ammonium chloride is a reversible reaction
• When heated, ammonium chloride breaks down from a white solid to the gases ammonia and hydrogen chloride - the forward reaction
• When cooled, the ammonia and hydrogen chloride react to re-form the white solid - the backward reaction