Question

How much percent is dry air in the atmosphere.
A. 100%
B. 99%
C. 78%
D. 90%

Answer 1

Hint: The air that covers the earth is the atmosphere. It's a mixture of distinct gases. It includes life-giving gases, such as oxygen which is used by animals and humans and carbon dioxide which is essential for plant growth. It envelops all over the world and is held in place by the earth's gravity.

Complete answer:
There are five primary layers of the Earth's atmosphere: the exosphere, the thermosphere, the mesosphere, the stratosphere, and the troposphere. In each higher layer, the atmosphere thins out until the gases in space dissipate.

In earth’s atmosphere Nitrogen, oxygen, and argon are the three main components of the Earth's atmosphere. By density, water vapour accounts for about 0.25 percent of the atmosphere. The water vapour (which is a greenhouse gas) concentration ranges considerably from around 10 ppm by volume in the coldest areas of the atmosphere to up to 5 percent by volume in warmer, humid air masses, and other atmospheric gas concentrations are usually quoted in terms of dry air (which is without water vapour).

Dry air has 78.09% of nitrogen, 20.95% of oxygen, 0.93% of argon, 0.04% of carbon dioxide, and small quantities of other gases by volume. This means that the whole of the atmosphere is made of about 99 percent of dry air.

Thus from the above discussion, it is clear that the correct answer is option ‘B’ that is 99%.

Note: Until about 2.4 billion years ago, the atmosphere had no oxygen at all. Microscopic existence, including photosynthesizing cyanobacteria, has nevertheless been well-established. These species have changed the planet's atmosphere by producing oxygen by photosynthesis. Much of their lives were anaerobic at the time, for which oxygen can be toxic. Thus, while this occurrence made the world today habitable for us, it also saw the first mass extinction of the Universe.