Question

The weakest reducing agent among the following is:
A. hydrogen gas.
B. coke.
C. carbon monoxide gas.
D. aluminium metal.

Answer 1

Hint: To solve this question, we have to remember that if the standard reduction potential of a substance is higher, then it is the best oxidising agent and if the standard reduction potential of a substance is lower, then it is the best reducing agent.

Complete step by step answer:
Here, we have to find out the weakest reducing agent,
We can say that the substance which is the best oxidising agent will be the weakest reducing agent.
As we know that, the standard reduction potential of coke, carbon monoxide gas and aluminium metal is a negative value.
Standard reduction potential of these substance are:
Aluminium metal = -1.33 V.
Carbon monoxide gas = -0.12 V and also,
Coke has a negative standard electrode potential.
Whereas, hydrogen gas has zero electrode potential.
This value is greater than the other negative values.
Therefore, hydrogen gas has the highest electrode potential, so it is the best oxidising agent or we can say that weakest reducing agent.
So, the correct answer is “Option A”.

Note: The substance which gives hydrogen for reduction is called reducing agent and the substance which removes oxygen is also called a reducing agent. The substance which gives oxygen for oxidation is called an oxidising agent and the substance which removes hydrogen is also called an oxidising agent.