A solution of substance X is used for white washing.

(i) Name the substance X and write its formula.

(ii) Write the reaction of the substance X named in (i) above with water.

In the refining of silver, the recovery of silver from silver nitrate solution involved "displacement by copper metal. Write down the reaction involved.

A shiny brown coloured element X on heating in the air becomes black in colour. Name the element X and the black coloured compound formed.

Why does the colour of copper sulphate solution change when an iron nail is dipped in it?

Identify the substances that are oxidised and the substances that are reduced in the following reactions:

(i) 4Na (s) + O₂ (g) → 2Na₂0 (s)

(ii) CuO (s) + H₂ (g) → Cu (s) + H₂O (l)