Question

Which of these reactions are redox reactions?
1.) $6NO(g)+4N{{H}_{3}}(g)\to 5{{N}_{2}}(g)+6{{H}_{2}}O(g)$
2.) $2S{{O}_{2}}(g)+{{O}_{2}}(g)\to 2S{{O}_{3}}(g)$
3.) $S{{O}_{3}}(g)+{{H}_{2}}O(g)\to {{H}_{2}}S{{O}_{4}}(g)$
A.) 1, 2 and 3 are correct
B.) 1 and 2 only are correct
C.) 2 and 3 only are correct
D.) 1 is only correct

Answer 1

As we know that a redox reaction is a type of reaction in which the transfer of electrons takes place from one of the reactants to another reactant. Or we can say that one behaves as a reducing agent, whereas another behaves as an oxidising agent.

Complete Solution :
- As we know that in any chemical reaction in which the electrons are transferred between the atoms that are basically involved as reactants is called a redox reaction. We can see that in oxidation loss of electrons takes place or we can say gain of oxygen takes place. Whereas, in reduction, gain of electrons takes place or we can say gain of hydrogen takes place.
- It is also found that the oxidising agent can gain electrons and itself get reduced in the reaction. Whereas, reducing agent loses electrons and gets oxidised itself.
- In the first reaction, $6NO(g)+4N{{H}_{3}}(g)\to 5{{N}_{2}}(g)+6{{H}_{2}}O(g)$ we can see that NO is an oxidising agent and $N{{H}_{3}}$ is a reducing agent. And both the process of oxidation and reduction is taking place.
- In the second reaction, $2S{{O}_{2}}(g)+{{O}_{2}}(g)\to 2S{{O}_{3}}(g)$,both the process of oxidation and reduction is taking place. In this reaction $S{{O}_{2}}$ is a reducing agent and ${{O}_{2}}$ is an oxidising agent.
- In the third reaction $S{{O}_{3}}(g)+{{H}_{2}}O(g)\to {{H}_{2}}S{{O}_{4}}(g)$, we can see that no reduction or oxidation is taking place.
So, the correct answer is “Option B”.

Note: - As we know that there is a special type of reaction called a disproportionation reaction, in which the same substance is found to both get oxidised or get reduced. For example in the reaction: $H{{g}_{2}}C{{l}_{2}}\to Hg+HgC{{l}_{2}}$
- Here, we can see that mercury is present in the form of $H{{g}^{+}}$, and it gets oxidised into $H{{g}^{2+}}$ and gets reduced into Hg.