Which of the following statements are wrong ?

Options

A. Reduction involves gain of electrons .
B. The oxidation number of reducing agent decreases.
C. Oxidising agent helps to increases the oxidation number of reducing agent.
D. Oxidation involves gain of electrons.

Answer

To determine which statements are wrong regarding redox reactions, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Statement 1: Reduction involves the gain of electrons.**
- **Analysis:** This statement is correct. Reduction is defined as the process where a species gains electrons, which leads to a decrease in its oxidation state.
- **Conclusion:** This statement is not wrong.

2. **Statement 2: The oxidation number of the reducing agent decreases.**
- **Analysis:** A reducing agent donates electrons to another species, thereby undergoing oxidation itself. When a reducing agent is oxidized, its oxidation number increases, not decreases.
- **Conclusion:** This statement is wrong.

3. **Statement 3: Oxidizing agent helps to increase the oxidation number of the reducing agent.**
- **Analysis:** An oxidizing agent accepts electrons from the reducing agent, which results in the oxidation of the reducing agent. This means that the oxidizing agent increases the oxidation number of the reducing agent, which is correct.
- **Conclusion:** This statement is not wrong.

4. **Statement 4: Oxidation involves gain of electrons.**
- **Analysis:** This statement is incorrect. Oxidation is defined as the loss of electrons. Therefore, saying that oxidation involves gain of electrons is wrong.
- **Conclusion:** This statement is wrong.

### Final Answer:
The wrong statements are **Statement 2** and **Statement 4**.

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