Question

Which of the following substances is a good oxidizing agent?
A.Coke
B.Water
C.Hydrogen peroxide
D.Sulphur dioxide

Answer 1

Hint:
Oxidizing agent is defined as the chemical species that tends to oxidize other substances, that is it increases the oxidation state of the substance by losing its electrons.
In order to know which oxidizing agent is good we first need to know the oxidation state of the compound or molecule.

Complete step by step answer:
Oxidizing agents normally exist in the highest oxidation states thus it has a tendency to gain electrons and can undergo reduction.
Stronger the electron affinity, stronger will be the oxidizing agent.
A.Coke
It is a very good reducing agent at high temperatures because it is non-metal and can combine easily with oxygen.
B.Water
In the presence of strong electron donors it acts as an oxidizing agent. It acts as a reducing agent in the presence of strong electron acceptors. So water has neither strong oxidizing or reducing agents. It behaves according to the substance with which it is going to react.
C.Hydrogen peroxide
Even hydrogen peroxide can act as an oxidizing agent as well as a reducing agent. But comparatively it is a strong oxidizing agent especially in the acidic conditions. When it acts as an oxidizing agent its oxidation state changes from $ - 1$ to zero. When it acts as a reducing agent its oxidation state changes from $ - 1$ to $ - 2$ which is a more stable oxidation state of oxygen in hydrogen peroxide.
D.Sulphur dioxide
It acts as a reducing agent because it is in $ + 4$ oxidation state which later on is oxidized by halogen to form sulfuryl halides.
Therefore, hydrogen peroxide is a good reducing agent.
So, the correct answer is option C) Hydrogen peroxide.

Note:Hydrogen peroxide is comparatively a strong oxidizing agent especially in the acidic conditions. Halogens, peroxide and oxygen are good oxidizing agents. The strongest elemental oxidizing agent is fluorine because of its high electronegativity.