(i) Account for the following :
(a) White silver chloride turns grey in sunlight.
(b) Brown coloured copper powder on heating in air turns into black coloured substance.
(ii) What do you mean by
(a) Displacement reaction (b) Reduction reaction (c) Combination reaction ? Write balanced chemical equation.

Explanation

(i) (a) White coloured silver chloride undergoes decomposition in the presence of sunlight and forms silver (grey in colour) and chlorine.
`{:(2AgCl(s) overset("Sun light")to 2Ag(s) + Cl_(2)(g)),("(White)" " "" (Grey)"):}`
(b) Brown coloured copper powder on heating in air gets oxidised to copper oxide which is black in colour.
`{:(2Cu(s) + O_(2)(g) overset("heat")to 2CuO(s)),("(Brown) " " "" (Black)"):}`