Tag: composition of air

Questions Related to composition of air

The proportion of nitrogen in the open air is:

  1. $21$% by volume

  2. $50$% by weight

  3. $21$% by weight

  4. $78$% by volume

  5. $29$% by volume


Correct Option: D
Explanation:

The proportion of nitrogen in the open air is 78% by volume.
Note:
Air is a mixture of gases. The volume percent of nitrogen and oxygen are 78%and 21% respectively. Air also contains tiny amounts of carbon dioxide, argon, methane, ozone and water vapour.

Which of the following gases do not form part of the atmosphere?

  1. Nitrogen

  2. Chlorine

  3. Carbon idoxide

  4. Oxygen

  5. Ozone


Correct Option: B
Explanation:

Nitrogen$(N _2)$, Carbon dioxide$(CO _2)$, Oxygen$(O _2)$, Ozone$(O _3)$ are part of the atmosphere but chlorine$(Cl _2)$ is not a part of atmosphere.

So answer is B.

One molecule of oxygen is represented by the formula :

  1. $O$

  2. $ O _{2}$

  3. $2O$

  4. $ O _{3}$


Correct Option: B
Explanation:

Oxygen is a chemical element, with the symbol O. Several allotropes, or molecular forms, of it exist, but the three most common in our environment are molecular oxygen, or dioxide, O2

Glass panes usually appear hazy because:

  1. water vapour settling on the tiny dust particles

  2. of chemical reactions

  3. it is the property of all transparent substances

  4. they are old


Correct Option: A
Explanation:

Air contains some gases, water vapours and dust particles that stick to a transparent glass of windows and it appears hazy. 


This is because air is a composition which includes water vapour and some other dust particles that come and rest on the windows which are not wiped. That is why they look hazy.


Hence, option A is correct.

The correct ascending order of gases as per their composition in air is:

  1. oxygen < carbon dioxide < nitrogen

  2. hydrogen < oxygen < nitrogen

  3. nitrogen < hydrogen < oxygen

  4. oxygen < carbon dioxide < hydrogen


Correct Option: B
Explanation:

By volume dry air contains $78.09\%$ Nitrogen, $20.95\%$ Oxygen, $0.93\%$ Argon, $0.04\%$ Carbon dioxide and small traces of other gases.

Ascending order of gases as per their composition in air is-
Hydrogen $<$ Oxygen $<$ Nitrogen

The percentage of nitrogen in air is:

  1. 21%

  2. 0.1%

  3. 54%

  4. 78%


Correct Option: D
Explanation:

The percentage of Nitrogen in air is $78\%$.

The percentage of Oxygen in air is $21\%$
The percentage of Argon in air is $0.93\%$
The percentage of Carbon dioxide is $0.04\%$

Air is regarded as a mixture because:

  1. its pressure may vary

  2. its temperature may change

  3. iis volume changes under different conditions

  4. its composition may vary


Correct Option: D
Explanation:

Air is composed of various gases in different proportions which can be separated using chemical methods.

Which gas has the highest partial pressure in atmosphere?

  1. $CO _2$

  2. $H _2O$

  3. $O _2$

  4. $N _2$


Correct Option: D
Explanation:

Air contains 78% Nitrogen. So, it contributes more no. of moles to partial pressure than any other gas in the atmosphere. So, it has the highest partial pressure. 

Which of the following compound does not exist ?

  1. $H _2$

  2. $He _2$

  3. $N _2O$

  4. $H _2O$


Correct Option: B
Explanation:

The compound compound $ He$ is chemically unreactive (inert) and do not forms compound under normal reaction conditions.$He _2$ does not exist.

A greenhouse gas that absorbs energy and maintains earth's temperature is :

  1. carbon dioxide

  2. nitrogen

  3. ozone

  4. oxygen


Correct Option: A
Explanation:

A greenhouse gas that absorbs energy and maintains earth's temperature is carbon dioxide.