Question

The proportion of nitrogen in the open air is:
A.21% by volume
B.50% by weight
C.21% by weight
D.78% by volume
E.29% by volume

Answer 1

Hint: The abundance of nitrogen in the atmosphere of the earth is greater than that of oxygen. The percentage of nitrogen gas is highest among all the gases present in the earth’s atmosphere. In other words, it is the most abundant gas in the earth’s atmosphere.

Complete step by step answer:
We are surrounded by air everywhere on this planet earth. The existence of life on the planet earth cannot be imagined without the existence of air. But what is air made up of? Is air a pure substance or a mixture? Earlier, it was thought that air was a pure substance, but later on it was found to be a mixture of many gases.
Air is actually the layer of gases which constitute the atmosphere of the earth. This layer of gases is retained by the gravity of the earth and is surrounding the earth forming its planetary atmosphere.
The composition of air differs from place to place. It is not constant everywhere. The main constituents of air are water vapor, oxygen, nitrogen, carbon dioxide and smoke and dust particles. Air comprises about 21% oxygen by volume. Nitrogen gas occupies almost 78% of earth’s atmosphere by volume and is thereby, the most abundant gas on planet earth. It is also the most abundant uncombined element.

Thus, the correct option is D.

Note:
The nitrogen gas is mainly used as an inert atmosphere whenever there is any possibility that the oxygen in air would cause a fire, explosion or oxidizing hazard.
It is combined with carbon dioxide to nitrogenate and to preserve the freshness of packaged foods.
It is also used as a cheap alternative to argon in incandescent light bulbs.