The actual density of nitrogen is $1.25\mathrm{ }\mathrm{g}/\mathrm{lit}$. The density of nitrogen obtained from the atmosphere is $1.257\mathrm{ }\mathrm{g}/\mathrm{lit}$. This is because of the fact that atmospheric nitrogen contains

Given data:

The actual density of nitrogen given is $1.25\mathrm{ }\mathrm{g}/\mathrm{lit}$. The density of nitrogen obtained from the atmosphere is $1.257\mathrm{ }\mathrm{g}/$ lit. The gas which is contained in atmospheric nitrogen is asked to be identified.

Formula/concept: Noble gas

Detailed solution:

The actual density of nitrogen is $1.25\mathrm{ }\mathrm{g}/\mathrm{lit}$. The density of nitrogen obtained from the atmosphere is $1.257\mathrm{ }\mathrm{g}/\mathrm{lit}$. This is due to the presence of argon and other noble gases in the atmospheric nitrogen.

Due to the presence of noble gases, a slight increase in density is seen (air in the atmosphere contains $1\%$ noble gases along with other common gases).