Which of the following molecules can act as an oxidising agent as well as a reducing agent ?

Options

A. `H_(2)S`
B. `SO_(3)`
C. `H_(2)O_(2)`
D. `F_(2)`

Answer

To determine which of the following molecules can act as both an oxidizing agent and a reducing agent, we will analyze each option step by step based on their oxidation states and electronic configurations.

### Step 1: Analyze H2S
- **Oxidation State**: In H2S, sulfur (S) has an oxidation state of -2.
- **Electronic Configuration**: The electronic configuration of sulfur is 1s² 2s² 2p⁶ 3s² 3p⁴. When sulfur is in the -2 state, it gains 2 electrons, achieving the configuration of 1s² 2s² 2p⁶ (noble gas configuration).
- **Oxidizing/Reducing Ability**:
- Since sulfur is already at a stable configuration, it cannot be reduced further (it cannot gain more electrons).
- However, it can be oxidized to higher oxidation states (+4 or +6).
- **Conclusion**: H2S can act as a reducing agent but not as an oxidizing agent.

### Step 2: Analyze SO3
- **Oxidation State**: In SO3, sulfur has an oxidation state of +6.
- **Electronic Configuration**: The configuration of sulfur in this state is 1s² 2s² 2p⁶ 3s² 3p⁴, losing 6 electrons.
- **Oxidizing/Reducing Ability**:
- Sulfur in the +6 state cannot be oxidized further.
- It can be reduced to lower oxidation states (+4, 0, or -2).
- **Conclusion**: SO3 can act as an oxidizing agent but not as a reducing agent.

### Step 3: Analyze H2O2
- **Oxidation State**: In H2O2, the oxidation state of oxygen is -1.
- **Electronic Configuration**: The electronic configuration of oxygen is 1s² 2s² 2p⁴. In the -1 state, it gains one electron (1s² 2s² 2p⁵).
- **Oxidizing/Reducing Ability**:
- H2O2 can be oxidized to O2 (0 oxidation state) and can also be reduced to water (H2O, -2 oxidation state).
- **Conclusion**: H2O2 can act as both an oxidizing agent and a reducing agent.

### Step 4: Analyze F2
- **Oxidation State**: In F2, the oxidation state of fluorine is 0.
- **Electronic Configuration**: The configuration of fluorine is 1s² 2s² 2p⁵. It can gain one electron to become F⁻ (-1 oxidation state).
- **Oxidizing/Reducing Ability**:
- F2 can be reduced to F⁻.
- However, it cannot be oxidized to F⁺ because fluorine has the highest electronegativity and does not easily lose electrons.
- **Conclusion**: F2 can act as a reducing agent but not as an oxidizing agent.

### Final Conclusion
Among the given options, only **H2O2 (hydrogen peroxide)** can act as both an oxidizing agent and a reducing agent.