Write the types of decomposition reactions with suitable examples.
Decomposition reactions can be classified into three types:
i) Thermal decomposition - such reactions are usually endothermic, since energy in the form of heat is required to break the bonds of the more complex molecule. Examples include
CaCO3(s)+heat→CaO(s)+CO2(g)
- calcium carbonate decomposes into calcium oxide and carbon dioxide when heated.
ii) Electrolytic decomposition - such reactions occur when an electric current is passed through an aqueous solution of a compound. Two classic examples are the electrolysis of water
2H2O(l)→2H2(g)+O2(g) - water decomposes into hydrogen and oxygen in the presence of an electric current;
and the decomposition of sodium chloride
2NaCl(l)→2Na(l)+Cl2(g) - molten sodium chloride will decompose into molten sodium and chlorine gas;
iii) Photo decomposition - these reactions occur in the presence of light (photons). Examples include
2AgCl(s)+sunlight→2Ag(s)+Cl2(g) - silver chloride decomposes into silver and chlorine in the presence of sunlight;
2AgBr(s)+sunlight→2Ag(s)+2Cl2(g) - silver bromide decomposes into silver and chlorine in the presence of sunlight.
Decomposition reactions can be classified into three types:
i) Thermal decomposition - such reactions are usually endothermic, since energy in the form of heat is required to break the bonds of the more complex molecule. Examples include
CaCO3(s)+heat→CaO(s)+CO2(g)
- calcium carbonate decomposes into calcium oxide and carbon dioxide when heated.
ii) Electrolytic decomposition - such reactions occur when an electric current is passed through an aqueous solution of a compound. Two classic examples are the electrolysis of water
2H2O(l)→2H2(g)+O2(g) - water decomposes into hydrogen and oxygen in the presence of an electric current;
and the decomposition of sodium chloride
2NaCl(l)→2Na(l)+Cl2(g) - molten sodium chloride will decompose into molten sodium and chlorine gas;
iii) Photo decomposition - these reactions occur in the presence of light (photons). Examples include
2AgCl(s)+sunlight→2Ag(s)+Cl2(g) - silver chloride decomposes into silver and chlorine in the presence of sunlight;
2AgBr(s)+sunlight→2Ag(s)+2Cl2(g) - silver bromide decomposes into silver and chlorine in the presence of sunlight.
