In which of the following processess is nitrogen oxidised ?

Options

A. `NH_(4)^(o+)rarrN_(2)`
B. `NO_(3)^(ө)rarrNO`
C. `NO_(2)rarrNO_(2)^(ө)`
D. `NO_(3)^(ө)rarrNH_(4)^(ө)`

Explanation

To determine in which of the given processes nitrogen is oxidized, we need to analyze the oxidation states of nitrogen in each process. Oxidation is defined as the loss of electrons, which corresponds to an increase in oxidation state.

Let's go through the processes step by step:

### Step 1: Analyze the first process
- **Process**: NH4+ → N2
- **Oxidation State of Nitrogen in NH4+**: In ammonium (NH4+), nitrogen has an oxidation state of -3.
- **Oxidation State of Nitrogen in N2**: In molecular nitrogen (N2), nitrogen has an oxidation state of 0.
- **Change in Oxidation State**: From -3 to 0, nitrogen is losing electrons (increasing oxidation state).
- **Conclusion**: Nitrogen is oxidized in this process.

### Step 2: Analyze the second process
- **Process**: NO3- → NO2
- **Oxidation State of Nitrogen in NO3-**: In nitrate (NO3-), nitrogen has an oxidation state of +5.
- **Oxidation State of Nitrogen in NO2**: In nitrogen dioxide (NO2), nitrogen has an oxidation state of +4.
- **Change in Oxidation State**: From +5 to +4, nitrogen is gaining electrons (decreasing oxidation state).
- **Conclusion**: Nitrogen is reduced in this process.

### Step 3: Analyze the third process
- **Process**: NO2 → NO
- **Oxidation State of Nitrogen in NO2**: In nitrogen dioxide (NO2), nitrogen has an oxidation state of +4.
- **Oxidation State of Nitrogen in NO**: In nitric oxide (NO), nitrogen has an oxidation state of +2.
- **Change in Oxidation State**: From +4 to +2, nitrogen is gaining electrons (decreasing oxidation state).
- **Conclusion**: Nitrogen is reduced in this process.

### Step 4: Analyze the fourth process
- **Process**: NO3- → NH4+
- **Oxidation State of Nitrogen in NO3-**: In nitrate (NO3-), nitrogen has an oxidation state of +5.
- **Oxidation State of Nitrogen in NH4+**: In ammonium (NH4+), nitrogen has an oxidation state of -3.
- **Change in Oxidation State**: From +5 to -3, nitrogen is gaining electrons (decreasing oxidation state).
- **Conclusion**: Nitrogen is reduced in this process.

### Final Conclusion
From the analysis above, we can conclude that nitrogen is oxidized only in the first process (NH4+ → N2).

### Answer
The correct answer is **option A: NH4+ → N2**.

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