Carbon Dioxide from Thermal Decomposition (Edexcel IGCSE Chemistry: Double Science)

What is thermal decomposition?

• Thermal decomposition is the term used to describe reactions where a substance breaks down due to the action of heat
• One such reaction is the thermal decomposition of metal carbonates
• Carbonates of metals from the lower half of the reactivity series tend to decompose on heating to produce the metal oxide and carbon dioxide gas:

metal carbonate → metal oxide + carbon dioxide

Thermal decomposition of copper(II) carbonate

The thermal decomposition of copper(II)carbonate produces copper(II) oxide and carbon dioxide

• The thermal decomposition of copper(II)carbonate occurs readily on heating
• Copper(II) carbonate is a green powder and slowly darkens as black copper(II) oxide is produced
• The carbon dioxide given off can be tested by passing the gas through limewater and looking for it to turn milky
• The equation for the reaction is

CuCO₃ (s) →  CuO (s)+ CO₂  (g) 

copper(II) carbonate → copper(II) oxide + carbon dioxide