In which process does the nitrogen undergo oxidation?

Options

A. `N_(2) to 2NH_(3)`
B. `N_(2)O_(4) ot 2NO_(2)`
C. `NO_(3)^(-) to N_(2)O_(5)`
D. `NO_(2)^(-) to NO_(3)^(-)`

Explanation

To determine in which process nitrogen undergoes oxidation, we need to analyze the oxidation states of nitrogen in different reactions. Oxidation is defined as the loss of electrons or an increase in oxidation number. Let's evaluate each option step by step.

### Step 1: Analyze the first reaction (N2 to NH3)
- **Initial State (N2)**: Nitrogen in N2 has an oxidation state of 0.
- **Final State (NH3)**: In NH3, the oxidation state of nitrogen can be calculated as follows:
\[ x + 3(+1) = 0 \implies x + 3 = 0 \implies x = -3 \]
- **Change in Oxidation State**: From 0 to -3 (gain of electrons).
- **Conclusion**: This is a reduction process, not oxidation.

### Step 2: Analyze the second reaction (N2O4 to 2NO2)
- **Initial State (N2O4)**: Let's assign oxidation states.
\[ 2x + 4(-2) = 0 \implies 2x - 8 = 0 \implies 2x = 8 \implies x = +4 \]
- **Final State (NO2)**:
\[ x + 2(-2) = 0 \implies x - 4 = 0 \implies x = +4 \]
- **Change in Oxidation State**: From +4 to +4 (no change).
- **Conclusion**: No oxidation occurs.

### Step 3: Analyze the third reaction (NO3- to N2O5)
- **Initial State (NO3-)**:
\[ x + 3(-2) = -1 \implies x - 6 = -1 \implies x = +5 \]
- **Final State (N2O5)**:
\[ 2y + 5(-2) = 0 \implies 2y - 10 = 0 \implies 2y = 10 \implies y = +5 \]
- **Change in Oxidation State**: From +5 to +5 (no change).
- **Conclusion**: No oxidation occurs.

### Step 4: Analyze the fourth reaction (NO2- to NO3-)
- **Initial State (NO2-)**:
\[ x + 2(-2) = -1 \implies x - 4 = -1 \implies x = +3 \]
- **Final State (NO3-)**:
\[ y + 3(-2) = -1 \implies y - 6 = -1 \implies y = +5 \]
- **Change in Oxidation State**: From +3 to +5 (loss of electrons).
- **Conclusion**: This is an oxidation process.

### Final Conclusion
The process in which nitrogen undergoes oxidation is the conversion of **NO2- to NO3-**, where nitrogen's oxidation state increases from +3 to +5.