Amongst the following which is a redox reaction ?

Options

A. `N_2 + O_2 rarr` (at
2000K)
B. Formation of `O_3` from `O_2`
C. Reaction between NaOH and `H_2SO_4`
D. Reaction between `AgNO_3` and NaCl

Answer

To determine which of the given reactions is a redox reaction, we need to identify if there is a simultaneous occurrence of oxidation and reduction in each reaction. A redox reaction involves the transfer of electrons, where oxidation is the loss of electrons and reduction is the gain of electrons.

Let's analyze each of the reactions step by step:

### Step 1: Understand Redox Reactions
- **Redox Reaction**: A reaction where oxidation and reduction occur simultaneously.
- **Oxidation**: Loss of electrons (increase in oxidation state).
- **Reduction**: Gain of electrons (decrease in oxidation state).

### Step 2: Analyze Each Reaction

#### Reaction 1: N2 + O2 → 2 NO (at 2000 K)
- **Oxidation States**:
- N2: Oxidation state of nitrogen is 0.
- O2: Oxidation state of oxygen is 0.
- NO: Oxidation state of nitrogen is +2, and oxygen is -2.
- **Change**:
- Nitrogen goes from 0 to +2 (oxidation).
- Oxygen goes from 0 to -2 (reduction).
- **Conclusion**: Both oxidation and reduction occur. **This is a redox reaction.**

#### Reaction 2: 3 O2 → 2 O3
- **Oxidation States**:
- O2: Oxidation state of oxygen is 0.
- O3: Oxidation state of oxygen is also 0 (in elemental form).
- **Change**: No change in oxidation states.
- **Conclusion**: No oxidation or reduction occurs. **This is not a redox reaction.**

#### Reaction 3: 2 NaOH + H2SO4 → Na2SO4 + 2 H2O
- **Oxidation States**:
- NaOH: Na is +1, O is -2, H is +1.
- H2SO4: H is +1, S is +6, O is -2.
- Na2SO4: Na is +1, S is +6, O is -2.
- H2O: H is +1, O is -2.
- **Change**: No change in oxidation states.
- **Conclusion**: No oxidation or reduction occurs. **This is not a redox reaction.**

#### Reaction 4: AgNO3 + NaCl → AgCl + NaNO3
- **Oxidation States**:
- AgNO3: Ag is +1, N is +5, O is -2.
- NaCl: Na is +1, Cl is -1.
- AgCl: Ag is +1, Cl is -1.
- NaNO3: Na is +1, N is +5, O is -2.
- **Change**: No change in oxidation states.
- **Conclusion**: No oxidation or reduction occurs. **This is not a redox reaction.**

### Final Conclusion
The only redox reaction among the given options is:
- **N2 + O2 → 2 NO** (This is a redox reaction).