Give reason:

Hydrogen is not used in balloons inspite of being the lightest gas.

Give reason:

It is difficult to find absolutely pure water in nature.

Give reason:

On boiling, water loses its taste.

Give reason:

Reagent silver nitrate is not prepared in tap water.

What do you observe:

Carbon dioxide is passed through lime water, first a little then in excess.

What do you observe:

Sulphur dioxide is passed through acidified ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ solution.

What do you observe:

Hydrochloric acid is added to lead nitrate solution.

What do you observe:

A piece of moist blue litmus paper is placed in a gas jar of chlorine.

What do you observe:

Iodine crystals are heated strongly in a test tube.