Question

Explain the following with the help of balanced chemical equation:
a. Bleaching action of SO₂.
b. Dehydration of formic acid by concentrated H₂SO₄.
c. Burning of benzene in presence of excess of dioxygen.

Answer 1

a. Bleaching action of SO₂:
SO₂ is used as a bleaching agent in presence of moisture. It bleaches due to reduction and bleaching action is temporary.
\[\ce{\underset{\text{Sulphur dioxide}}{SO_2} + \underset{\text{water}}{2H_2O} -> \underset{\text{Sulphuric acid}}{H_2SO_4} + 2(H)}\]

b. Dehydration of formic acid by concentrated H₂SO₄:
Concentrated H₂SO₄ acts as a powerful dehydrating agent due to strong affinity for water.
\[\ce{\underset{\text{Formic acid}}{HCOOH} ->[Conc. H_2SO_4] \underset{\text{Carbon monoxide}}{CO} + \underset{\text{Water}}{H_2O}}\]

c. Burning of benzene in presence of excess of dioxygen:
Combustion of benezene in excess of dioxygen (air) results in the formation of carbon dioxide and water.
\[\ce{ \underset{\text{Benzene}}{C_6H_6} + \underset{\text{Dioxygen}}{15/2O_2} -> \underset{\text{Carbon dioxide}}{6CO_2} + \underset{\text{Water}}{3H_2O}}\]