Which of the following reactions is/are not intermolecular redox reaction?

Options

A. `PbO_(2)+H_(2)OtoPbO+H_(2)O_(2)`
B. `2KClO_(3)to2KCl+3O_(2)`
C. `(NH_(4))_(2)Cr_(2)O_(7)toN_(2)+Cr_(2)O_(3)+4H_(2)O`
D. `NH_(4)NH_(2)toN_(2)+2H_(2)O`

Explanation

To determine which of the given reactions are not intermolecular redox reactions, we need to understand the concept of intermolecular and intramolecular redox reactions.

### Step-by-Step Solution:

1. **Understanding Redox Reactions**:
- Redox reactions involve the transfer of electrons between two species, leading to oxidation (loss of electrons) and reduction (gain of electrons).
- In intermolecular redox reactions, oxidation and reduction occur between different molecules.

2. **Identifying Intramolecular vs. Intermolecular**:
- In intramolecular redox reactions, both oxidation and reduction occur within the same molecule.
- In intermolecular redox reactions, one molecule is oxidized while another is reduced.

3. **Analyzing the Given Reactions**:
- **Reaction 1**: PbO2 + H2O → PbO + H2O2
- In this reaction, lead (Pb) is reduced from +4 to +2, and oxygen (O) is oxidized from -2 to -1. Since different species are involved in oxidation and reduction, this is an intermolecular redox reaction.

- **Reaction 2**: KClO3 → 2KCl + 3O2
- In this reaction, chlorine (Cl) is reduced from +5 to -1, and oxygen (O) is oxidized from -2 to 0. However, both processes occur within the same compound (KClO3). Thus, this is not an intermolecular redox reaction.

- **Reaction 3**: (Similar to Reaction 2)
- If another reaction follows the same pattern as KClO3 (where oxidation and reduction occur within the same molecule), it will also be classified as not an intermolecular redox reaction.

4. **Conclusion**:
- Based on the analysis, the reactions that are not intermolecular redox reactions are:
- Reaction 2 (KClO3 → 2KCl + 3O2)
- Any other reactions that follow the same pattern as Reaction 2.

### Final Answer:
The reactions that are not intermolecular redox reactions are **Reaction 2 and any similar reactions**.