Question

What are the oxidizing agent and the reducing agent in this chemical equation? 3FeS + 8HNO3 → 3FeSO4 + 8NO + 4H2O

Answer 1

Answer: The reducing agent is FeS and the oxidizing agent is $HNO_3$

Explanation:

Oxidizing agent is defined as the agent which oxidizes the other substance and itself gets reduced. It undergoes reduction reaction which means it gains electrons and the oxidation state of the substance gets reduced.

Reducing agent is defined as the agent which reduces the other substance and itself gets oxidized. It undergoes oxidation reaction which means it looses electrons and the oxidation state of the substance is increased.

For the given chemical equation:

$3FeS+8HNO_3\rightarrow 3FeSO_4+8NO+4H_2O$

On reactant side:

Oxidation state of Iron = +2

Oxidation state of Sulfur = -2

Oxidation state of oxygen = -2

Oxidation state of hydrogen = +1

Oxidation state of nitrogen = +5

On product side:

Oxidation state of Iron = +2

Oxidation state of Sulfur = +6

Oxidation state of oxygen = -2

Oxidation state of hydrogen = +1

Oxidation state of nitrogen = +2

As, oxidation state of Sulfur is increasing from -2 to +6, it is loosing electrons and thus it is undergoing oxidation reaction and FeS is considered as a reducing agent. And the oxidation state of Nitrogen in reducing from +5 to +2, it is gaining electrons and thus it is undergoing reduction reaction and $HNO_3$ is considered as an oxidizing agent.

Thus, The reducing agent is FeS and the oxidizing agent is $HNO_3$

Answer 2

The oxidizing agent is one which itself gets reduced and oxidizes other

Reduction : in this process the element accepts electron and gets reduced

Reducing agent is one which itself gets oxidized and reduces other

Oxidation : in this process the element loses electron and gets oxidized

Here the oxidation number of Sulphur change  from -2 (FeS) to +6 (FeSO4) so it is oxidized and thus it is the reducing agent

The oxidation number of nitrogen changes from +5 (HNO3) to +2 (NO) thus it is reduced and thus it is the oxidizing agent