Group 2: Thermal Decomposition of Nitrates & Carbonates
- Thermal decomposition is the breakdown of a compound into two or more different substances using heat
Thermal decomposition of carbonates
- The Group 2 carbonates break down (decompose) when they are heated to form the metal oxide and give off carbon dioxide gas
- The general equation for the decomposition of Group 2 carbonates is:
The thermal decomposition of magnesium carbonate to form magnesium oxide and carbon dioxide gas
Thermal decomposition of nitrates
- The Group 2 nitrates break decomposed when they are heated to form the metal oxide, oxygen gas and nitrogen dioxide gas (which is a brown toxic gas)
- Since the formed nitrogen dioxide gas is toxic, the decomposition of nitrates is often carried out in a fume cupboard
The diagram shows the thermal decomposition of magnesium nitrate to form magnesium oxide, oxygen gas and nitrogen dioxide gas
- The general equation for the decomposition of Group 2 nitrates is:
- Going down the group, more heat is needed to break down the nitrates
- The smaller positive ions at the top of Group II will polarise the nitrate ions more than the larger ions at the bottom of the group
- The more polarised they are, the more likely they are to thermally decompose