On heating copper powder in air the surface of copper powder becomes coated with black CuO . How can this black coating be converted into brown copper? Write a chemical equation for the reaction that occurs during the colour change.

Q. Identify the type of chemical reaction taking place and also write the balance chemical equation for : on heating copper powder in air is china dish, a surface of copper powder turns block.

Q. On heating blue coloured powder of copper(II) nitrate in a boiling tube copper oxide (black), oxygen gas and a brown gas X is formed. What is the balanced chemical equation for the reaction?

Q. When copper powder is heated it gets coated with :

Q. When heated in air, brown copper powder turns black. This black powder would turn brown again when heated with:

Q. You are given the following materials:
(i) Iron nails
(ii) Copper sulphate solution
(iii) Barium chloride solution
(iv) Copper powder
(v) Ferrous sulphate crystals
(vi) Quicklime

Identify the type of chemical reaction taking place when:
(a) Barium chloride solution is mixed with copper sulphate solution and a white precipitate is observed.
(b) On heating copper powder in air in a china dish, the surface of copper powder turns black.
(c) On heating green coloured ferrous sulphate crystals, reddish brown solid is left and smell of a gas having odour of burning sulphur is experienced.
(d) Iron nails when left dipped in blue colour copper sulphate solution become brownish in colour and the blue colour of copper sulphate fades away.
(e) Quick lime reacts vigorously with water releasing a large amount of heat.
Write chemical equations for each one of the above reactions.