Which of the following reaction involves oxidation reduction?

Options

A. `NaBr+HCItoNaCl+Br`
B. `HBrAgNO_(3)toAgBr+HNO_(3)`
C. `H_(2)+Br_(2)to2HBr`
D. `2NaOH+H_(2)SO_(4)toNa_(2)SO_(4)+2H_(2)O`

Explanation

To determine which of the given reactions involves oxidation and reduction (a redox reaction), we need to analyze the oxidation states of the elements involved in each reaction. A redox reaction is characterized by a change in oxidation states, indicating that oxidation (loss of electrons) and reduction (gain of electrons) are occurring simultaneously.

### Step-by-Step Solution:

1. **Analyze Option 1: NaBr + HCl → NaCl + Br2**
- Assign oxidation states:
- Na: +1 (in NaBr and NaCl)
- Br: -1 (in NaBr), 0 (in Br2)
- H: +1 (in HCl)
- Cl: -1 (in HCl and NaCl)
- Changes in oxidation states:
- Na: +1 to +1 (no change)
- Br: -1 to 0 (oxidation)
- H: +1 to +1 (no change)
- Cl: -1 to -1 (no change)
- **Conclusion**: No simultaneous oxidation and reduction. This is **not a redox reaction**.

2. **Analyze Option 2: HBr + AgNO3 → AgBr + HNO3**
- Assign oxidation states:
- H: +1 (in HBr)
- Br: -1 (in HBr and AgBr)
- Ag: +1 (in AgBr)
- N: +5 (in AgNO3 and HNO3)
- O: -2 (in both nitrates)
- Changes in oxidation states:
- H: +1 to +1 (no change)
- Br: -1 to -1 (no change)
- Ag: +1 to +1 (no change)
- N: +5 to +5 (no change)
- **Conclusion**: No change in oxidation states. This is **not a redox reaction**.

3. **Analyze Option 3: H2 + Br2 → 2HBr**
- Assign oxidation states:
- H: 0 (in H2), +1 (in HBr)
- Br: 0 (in Br2), -1 (in HBr)
- Changes in oxidation states:
- H: 0 to +1 (oxidation)
- Br: 0 to -1 (reduction)
- **Conclusion**: Oxidation and reduction are occurring simultaneously. This is a **redox reaction**.

4. **Analyze Option 4: Na2SO4 + BaCl2 → BaSO4 + 2NaCl**
- Assign oxidation states:
- Na: +1 (in Na2SO4 and NaCl)
- S: +6 (in Na2SO4)
- O: -2 (in Na2SO4)
- Ba: +2 (in BaSO4)
- Cl: -1 (in BaCl2 and NaCl)
- Changes in oxidation states:
- Na: +1 to +1 (no change)
- S: +6 to +6 (no change)
- O: -2 to -2 (no change)
- Ba: +2 to +2 (no change)
- Cl: -1 to -1 (no change)
- **Conclusion**: No change in oxidation states. This is **not a redox reaction**.

### Final Answer:
The reaction that involves oxidation and reduction is **Option 3: H2 + Br2 → 2HBr**.