Give reasons for the following :
(i) The blue colour of copper sulphate solution is rendered light green when a piece of iron is dropped into it.
(ii) Fried potato chips are often packed with nitrogen gas.
(iii) Cooked food emits a bad smell when left exposed to air for a day or two.

Give reasons for the following: Blue colour of copper sulphate solution is destroyed when iron filings are added to it.

Give reasons for the following : (i) Zinc can displace copper from copper sulphate solution. (ii) Silver articles become black after sometime when exposed to air. (iii) A metal sulphide is converted to its oxide to extract the metal from sulphide ore.

On keeping iron nails in a blue coloured copper sulphate solution, it is observed that the colour of the solution turns light green after sometime. Give reasons for this colour change. Name the type of reaction.

Give reasons for the following : (i) Carbonate and sulphide ores are converted into oxides before reduction. (ii) Aluminium is rendered passive when it is dipped in conc. HNO_(3) (iii) Nonmetals do not displace hydrogen from acids. (iv) An aqueous solution of CuSO_(4) cannot be stored in an iron vessel. (v) The surface of some metals become dull when left exposed to air for a long time.

Give reason for the following: (i). Silver ornament gets tarnished when exposed to atmosphere for a long time. (ii) Silver nitrate solution is kept in dark coloured bottles. (iii). Why does AgNO_3 produce a black stain on the skin.