Question

$S{O}_3$ can act as
(A) Oxidising agent
(B) Reducing agent
(C) Both a and b
(D) None

Answer 1

Hint :An oxidising agent gains electrons and gets reduced in a chemical reaction. A reducing agent loses electrons and it gets oxidised in a chemical reaction. A reducing agent is in one of its lowest possible oxidation states and is also called an electron donor.

Complete Step By Step Answer:
Sulphur trioxide is a chemical compound and it is represented by the chemical formula $S{O}_3$ . It exists in a number of modifications that differ in molecular species and in crystalline form. It is colourless in its liquid form. It is a highly reactive substance and also a strong oxidising agent. It also acts as a fire hazard. It is a thermodynamically unstable compound with respect to the compound selenium dioxide. In $S{O}_3$ sulphur is in $+6$ oxidation state which is its highest oxidation state. So, it cannot be oxidized further. Hence, it acts as a strong oxidizing agent and because of this $S{O}_3$ itself gets reduced and oxidised other compounds. $S{O}_3$ is not used as a reducing agent as it cannot donate a lone pair of electrons. The bleaching action of sulphur is based on the oxidation.
Therefore, option A is the correct answer.

Note :
 $S{O}_3$ is used as a bleaching agent to remove the residual hydrogen peroxide or as a digesting agent to separate the pulp from lignin. It is also used as a catalyst in the oxidation reaction of sulphur dioxide to sulphur trioxide. It is used in the manufacture of photoelectric cells and also solar energy devices.