Question

$NO_2$ gas is :

• A. Colourless, neutral
• B. Colourless, acidic
• C. Brown, acidic
• D. Brown, neutral

Hint:

NO2​ is a brown acidic gas forming nitric acid in water.

Answer 1

The Correct Option is C

The question asks about the characteristics of \(NO_2\) gas. To determine the correct answer, we need to consider both the color and the acidity of \(NO_2\) gas. 

1. Color: \(NO_2\) gas is known to be a reddish-brown gas. It is commonly observed in the atmosphere as a brown haze, especially in urban areas with high levels of pollution. Thus, the characterisation of \(NO_2\) gas as colorless is incorrect.
2. Acidity and Chemistry: \(NO_2\) is a nitrogen dioxide molecule, which is an acidic oxide of nitrogen. When it is dissolved in water, it leads to the formation of a mixture of nitric acid (\(HNO_3\)) and nitrous acid (\(HNO_2\)), making the solution acidic:

\(2NO_2 + H_2O \rightarrow HNO_3 + HNO_2\)

1. Considering the above properties, \(NO_2\) is acidic in nature.

Given the information, the correct characteristics of \(NO_2\) gas are:

Brown, acidic

This matches the option: Brown, acidic.