Question

in the electrolysis of water,
a) name the gas collected at anode and cathode
b) why is the volume off gas collected at one electrode double than the other?
c) what would happen if dil H2SO4 is not added to water?

Answer 1

When electric current is passed through water , it decomposes to give hydrogen gas and oxygen gas.

                 ELECTRICITY
2H₂O(I) ---------------------------- > 2H₂(g) + O₂(g)

At cathode :
H+ ions will gain electrons and form Hydrogen gas 

2H⁺ +2e--->H2 (g)

At anode : Oxygen gas will be released 

4 OH⁻(aq)→O2(g) + 2 H2O(l) + 4 e−

II) The volume of hydrogen gas collected at cathode is more than volume of oxygen gas at anode because water is made up of 2 parts of hydrogen and 1 part of oxygen by volume.

iii) If dil.H2SO4 is added to water then the rate of electrolysis increases.

Answer 2

Answer:

a ) The following gases are collected :

1) hydrogen : cathode

2) oxygen : anode

b) In the electrolysis of water, the gas collected at cathode is hydrogen and the gas collected at anode is oxygen. The gas which is collected in double amount is hydrogen. This is because water contains two molecules as compared to one molecule of oxygen.

The reaction that takes place in the formation of water from H2 and O2 is:

                    $2H_{2}O$ →  $2H_{2} +O_{2}$

C) if dil H2SO4 is not added to water, then water does not conduct electricity .  A few drops of dil.$H_{2} SO_{4}$ are added to make the water conducting.