Question

Which of the following is not an oxidising agent?
(A) Oxygen
(B) Conc. Sulphuric acid
(C) Chlorine
(D) Hydrogen

Answer 1

An oxidising agent is a chemical compound or an element that accepts electrons from another chemical compound or element to oxidise that compound and get reduced itself.

Complete step by step solution:
Let us look at the redox properties of the above given elements:
Oxygen – The oxidation number of oxygen is 0 in its free state, while its highest oxidation state is $\left( { - 2} \right)$ and so it has a tendency to accept electrons so it will behave as an oxidising agent.
Conc. Sulphuric acid – The major element in conc. Sulphuric acid is sulphur and its oxidation state in the molecule is $\left( { + 6} \right)$ which is the highest oxidation state of sulphur and hence it has the tendency to accept electrons and act as an oxidising agent.
Chlorine – In the elemental state, the oxidation state is (0) while its oxidation state can go upto $\left( { - 1} \right)$ hence it also has the tendency to accept electrons and behave as an oxidising agent.
Hydrogen – In the free state, the oxidation state of oxygen is (0) while hydrogen is mostly an electropositive and except for reaction with alkali metals, its oxidation state is mostly $\left( { + 1} \right)$ and hence hydrogen generally does not act as the oxidising agent.
Hence, the correct option is D.

Note:
The oxidation state of an element describes the tendency of the element to accept or lose electrons. It is generally 0 for elements in the elemental state or the free-state. If any element in its highest oxidation state then it will try to accept electrons and hence act as oxidising agent while if it is in its lowest oxidation state then it will act as reducing agent or if it has the tendency to lose electrons like the alkali metals.