In the reaction :-
`C+4HNO_(3)rarrCO_(2)+2H_(2)O+4NO_(2)`
`HNO_(3)` acts as :-

Options

A. An oxidising agent
B. An acid
C. A reducing agent
D. None of them

Answer

To determine the role of HNO3 in the given reaction, we need to analyze the oxidation states of the elements involved in the reaction. Let's break down the process step by step:

### Step 1: Write the balanced chemical equation
The reaction provided is:
\[ C + 4HNO_3 \rightarrow CO_2 + 2H_2O + 4NO_2 \]

### Step 2: Determine the oxidation states
- **For Carbon (C)**: In elemental form, the oxidation state of carbon is 0. In carbon dioxide (CO2), the oxidation state of carbon is +4.

- **For Nitrogen (N)**: In nitric acid (HNO3), we need to calculate the oxidation state of nitrogen. The formula for HNO3 can be analyzed as follows:
- Let the oxidation state of nitrogen be \( x \).
- The oxidation state of hydrogen is +1 and that of oxygen is -2.
- The equation for HNO3 is:
\[ x + 1 + 3(-2) = 0 \implies x + 1 - 6 = 0 \implies x = +5 \]
Thus, the oxidation state of nitrogen in HNO3 is +5.

- **For Nitrogen in NO2**: In nitrogen dioxide (NO2), the oxidation state of nitrogen can be calculated similarly:
- Let the oxidation state of nitrogen in NO2 be \( y \).
- The equation for NO2 is:
\[ y + 2(-2) = 0 \implies y - 4 = 0 \implies y = +4 \]
Thus, the oxidation state of nitrogen in NO2 is +4.

### Step 3: Analyze the changes in oxidation states
- **Carbon**: The oxidation state changes from 0 (in C) to +4 (in CO2). This indicates that carbon is oxidized.
- **Nitrogen**: The oxidation state changes from +5 (in HNO3) to +4 (in NO2). This indicates that nitrogen is reduced.

### Step 4: Identify the role of HNO3
Since HNO3 is causing the oxidation of carbon (which loses electrons) and itself gets reduced (which gains electrons), HNO3 acts as an oxidizing agent.

### Conclusion
Thus, in the reaction, HNO3 acts as an oxidizing agent.

### Final Answer
HNO3 acts as an oxidizing agent.

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