Identify the type of reactions taking place in each of the following: 

a. Barium chloride solution is mixed with copper sulphate solution and white precipitate is formed. 

b. On heating copper powder in china dish, the surface of copper powder turns black. 

c. On heating green coloured ferrous sulphate crystals, raddish brown solid is left and smell of a gas having odour of burning sulphur is experienced. 

d. Iron nails when left dipped in blue copper sulphate solution become reddish brown in colour and the blue colour of copper sulphate fades away. 

e. Quick lime reacts vigorously with water releasing a large amount of heat.