What is the possible product of the reaction in which 1 mole of `HNO_3` is reduced by absorption of 4 moles electrons?

Options

A. `0.5 "mole of" N_2`
B. `0.5 "mole" of N_2O`
C. 1 mole of `NO_3`
D. 1 mole of `NH_3`

Answer

To determine the possible product of the reaction in which 1 mole of HNO3 (nitric acid) is reduced by the absorption of 4 moles of electrons, we can follow these steps:

### Step 1: Determine the oxidation state of nitrogen in HNO3
- The formula for nitric acid is HNO3.
- The oxidation state of hydrogen (H) is +1.
- The oxidation state of oxygen (O) is -2. Since there are three oxygen atoms, the total contribution from oxygen is 3 × (-2) = -6.
- The compound is neutral, so we can set up the equation:
\[ x + (+1) + (-6) = 0 \]
where \(x\) is the oxidation state of nitrogen (N).

### Step 2: Solve for the oxidation state of nitrogen
- Rearranging the equation gives:
\[ x - 5 = 0 \implies x = +5 \]
- Therefore, the oxidation state of nitrogen in HNO3 is +5.

### Step 3: Determine the change in oxidation state upon reduction
- When HNO3 is reduced by gaining 4 moles of electrons, the oxidation state of nitrogen changes from +5 to:
\[ +5 - 4 = +1 \]

### Step 4: Identify the possible product with nitrogen in the +1 oxidation state
- We need to find a compound where nitrogen has an oxidation state of +1. One such compound is N2O (nitrous oxide).
- The oxidation state of nitrogen in N2O can be calculated as follows:
- Let the oxidation state of nitrogen be \(x\). The oxidation state of oxygen is -2.
- The compound is neutral, so:
\[ 2x + (-2) = 0 \implies 2x = 2 \implies x = +1 \]
- Thus, the oxidation state of nitrogen in N2O is indeed +1.

### Step 5: Compare with other options
- Option A: 0.5 mole of N2O (correct, as we can produce N2O).
- Option C: 1 mole of NO3 (oxidation state of nitrogen is +5).
- Option D: 1 mole of NH3 (oxidation state of nitrogen is -3).

### Conclusion
- The possible product of the reaction is **0.5 mole of N2O**.

### Final Answer
- The correct answer is **Option A: 0.5 mole of N2O**.