The reddish -brown gas formed when nitric oxide is oxidized by air is

Options

A. `NO_(2)`
B. `N_(2)O_(4)`
C. `N_(2)O_(5)`
D. `N_(2)O_(3)`

Answer

To solve the question regarding the reddish-brown gas formed when nitric oxide is oxidized by air, we can follow these steps:

### Step 1: Identify the Reaction
We need to understand the reaction that occurs when nitric oxide (NO) is exposed to oxygen (O2) in the air.

### Step 2: Write the Chemical Equation
The reaction between nitric oxide and oxygen can be represented by the following balanced chemical equation:
\[ 2 \, \text{NO} + \text{O}_2 \rightarrow 2 \, \text{NO}_2 \]
This shows that two molecules of nitric oxide react with one molecule of oxygen to produce two molecules of nitrogen dioxide (NO2).

### Step 3: Identify the Product
From the balanced equation, we see that the product formed is nitrogen dioxide (NO2).

### Step 4: Determine the Color of the Gas
Nitrogen dioxide (NO2) is known to be a reddish-brown gas. This characteristic color is important for identifying the gas produced in the reaction.

### Conclusion
Thus, the reddish-brown gas formed when nitric oxide is oxidized by air is nitrogen dioxide (NO2).

### Final Answer
The correct answer is NO2.

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