Which one of the following is an example of disproportionation reaction?

Options

A. `3HClO_3rarrHClO_4+Cl_2+2O_2+H_2O`
B. `Mg+O_2rarr2MgO`
C. `PCl_5rarrPCl_3+Cl_2`
D. `CH_4+2O_2rarrCO_2+2H_2O`

Answer

To determine which reaction is an example of a disproportionation reaction, we first need to understand what a disproportionation reaction is.

### Step-by-Step Solution:

1. **Definition of Disproportionation Reaction**:
A disproportionation reaction is a specific type of redox reaction where a single substance is both oxidized and reduced, resulting in two different products.

2. **Identifying Oxidation States**:
To identify a disproportionation reaction, we need to look for a reactant that changes its oxidation state in the course of the reaction. For example, in the case of chlorine compounds, we can analyze the oxidation states of chlorine in different compounds.

3. **Example of Disproportionation**:
Consider the reaction of chlorine in HClO3 (chloric acid) and HClO4 (perchloric acid):
- In HClO3, chlorine has an oxidation state of +5.
- In HClO4, chlorine has an oxidation state of +7.
- In a disproportionation reaction, chlorine can also be reduced to a lower oxidation state, such as -1 in HCl (hydrochloric acid).

4. **Conclusion**:
The reaction where chlorine in HClO3 is oxidized to HClO4 (oxidation from +5 to +7) and reduced to HCl (reduction from +5 to -1) is an example of a disproportionation reaction.

### Final Answer:
An example of a disproportionation reaction is the reaction of chlorine in HClO3 where it is oxidized to HClO4 and reduced to HCl.

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