Carbon Dioxide from Thermal Decomposition (Edexcel IGCSE Science)

Spec point — 2.12 · describe the formation of carbon dioxide from the thermal decomposition of metal carbonates, including copper(II) carbonate

Thermal decomposition

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

Exam Hint The release of carbon dioxide from calcium carbonate in the production of cement is a contributing source of rising atmospheric CO₂ levels that contributes to the enhanced greenhouse effect.