In the electrolysis of water :
(i) Name the gas collected at the cathode and anode respectively.
(ii) Why is the volume of one gas collected at one electrode double than that at the other ?
(iii) How will you test the evolved gases ?

Explanation

(i) `H_(2)` gas is collected at cathode and `O_(2)` gas at anode.
(ii) The chemical equation for the electrolysis process is an follows :
`2H_(2)O(l) overset("Electrolysis")to underset("(2 vol.)")(2H_(2)(g)) + underset("(1 vol.)")(O_(2) (g))`
This clearly shows as to why the volume of one gas is double than that of the other.
(iii) Hydrogen gas burns with a pop sound when the burning splinter is brought near the gas. If a smoulding match stick is brought in contact with oxygen gas, it starts burning brightly.