Question

In the treatment of domestic water supplies, chlorine is added to the water to form chloric(I) acid,HClO.

Cl2(aq) + H2O(I) → H+(aq) + Cl–(aq) + HClO(aq)

The HClO reacts further to give the chlorate(I) ion.(CLO-)

HClO(aq) + H2O(I) → H3O+(aq) + ClO–(aq)

Both HClO and ClO–kill bacteria by oxidation.

What is the change in oxidation number of chlorine in forming the chlorate(I) ion from the aqueous chlorine?

PLEASE SHOW WORKING :)

Answer 1

Chlorine goes from Cl₂ to ClO⁻.

Oxidation state of Cl in Cl₂ is zero whereas in ClO⁻ it is +1. Hence change in oxidation state of Chlorine is 1.

Calculation of oxidation number of Cl in ClO⁻ or HClO⁻ :
Let x be oxidation number of Cl in ClO⁻ the. Now since the net charge on ClO⁻ is -1, sum of oxidation number of all must be equal to -1. 


Therefore,
x + (-2) = -1 .....[ oxidation number of O is -2]
∴ x = 2-1 = +1
Therefore oxidation number of Cl in ClO⁻ is +1