Question

When electricity is passed through water,bubbles of oxygen and hydrogen are respectively released at electrodes connected to -and - terminals of a cell.

Answer 1

During electrolysis, electricity is passed ( using positive and negative electrodes) through a solution or liquid that has ions which leads to chemical decomposition.

When the process of electrolysis is initiated, different elements are formed at the cathode( negative electrode) and the anode ( positive electrode), depending on:

i) The solution
ii) The position of the electrode or the anode in the reactivity series.

During the electrolysis of water of sulphuric acid, the products of the electrolysis are as follows: 

i) Oxygen is formed at the anode
ii) Hydrogen is formed at the cathode

Here are the equations of the reactions that take place during the process:

1) At the anode(+ve):

 6H₂O(l)  O₂(g) + 4H₃O⁺(aq) + 4e⁻ ( moves to the anode)

2) Cathode(-ve):

4e⁻(comes from cathode) + 4H₂O(l)   2H₂(g) + 4OH⁻(aq)

Answer 2

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

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

Water  splits up into H+ ions and OH- ions .
Positive H+ ions will move towards the negative terminal that is cathode and OH- ions will move towards anode.

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−