Tag: composition of air

Questions Related to composition of air

All the noble gases have $8$ electrons in their outermost shell except :

  1. $Ar$

  2. $Kr$

  3. $Ne$

  4. $He$


Correct Option: D
Explanation:

All the noble gases have 8 electrons in their outermost shell except  Helium (He) which has only 2 electrons in its outermost shell.

Most common inert gases are:

  1. Helium

  2. Krypton

  3. Argon

  4. All of above


Correct Option: D
Explanation:

When we refer to inert gases, we are usually referring to six primary ones, also called the noble gases. Meet the most common inert gases: helium $\left(He\right)$, argon $\left(Ar\right)$, neon $\left(Ne\right)$, krypton $\left(Kr\right)$, xenon $\left(Xe\right)$, and radon $\left(Rn\right)$.

The amount of water vapour in air is termed as:

  1. humidity.

  2. dew.

  3. mist.

  4. none of the above.


Correct Option: A
Explanation:

Humidity is the amount of water vapour in the atmosphere. It is a significant aspect of atmosphere beacuse it effects the weather and climate.

Why are some gases inert?

  1. They are stable

  2. They have 5 electrons in their last shell

  3. They do not have sufficient atoms to react

  4. All of above


Correct Option: A
Explanation:

Most atoms do not have 8 electrons in this outer orbital so they react with other atoms to form bonds to fill their outer electron orbital. The atomic structure of the noble gases is different from the structure of most atoms because they have a filled outer orbital.

Which of the following is used in balloons and airships?

  1. Argon

  2. Neon

  3. Helium

  4. Carbon


Correct Option: C
Explanation:

Helium is used in balloons and airships. It is much less dense than air, so balloons filled with it float upwards.

Nitrogen is liberated by the thermal decomposition of only :

  1. $NH _4NO _2$

  2. $NaN _3$

  3. $(NH _4) _2Cr _2O _7$

  4. All of these


Correct Option: A
Explanation:

$ { { (NH } _{ 2 }) } _{ 2 }{ Cr } _{ 2 }{ O } _{ 7 }\xrightarrow [ thermal\quad decomposition ]{ \Delta  } { Cr } _{ 2 }{ O } _{ 3 }+{ N } _{ 2 }+4{ H } _{ 2 }O\ N{ H } _{ 4 }{ NO } _{ 2 }\xrightarrow [ thermal\quad decomposition ]{ \Delta  } { N } _{ 2 }+2{ H } _{ 2 }O\ 2{ NaN } _{ 3 }\xrightarrow [ thermal\quad decomposition ]{ \Delta  } 2Na+3{ N } _{ 2 } $ 


Hence, all of these. 

Main constituent in air is:

  1. nitrogen

  2. oxygen

  3. argon

  4. water vapor


Correct Option: A
Explanation:

Main constituent in air is nitrogen.
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 noble gas is used in light bulbs?

  1. Helium

  2. Neon

  3. Krypton

  4. Argon


Correct Option: D
Explanation:

Argon is used in light bulbs. The very thin metal filament inside the bulb would react with oxygen and burn away if the bulb were filled with air instead of argon. Argon stops the filament burning away because it is unreactive.

Combustion can not take place without:

  1. water

  2. carbon

  3. air

  4. zinc


Correct Option: C
Explanation:

Combustion can not take place without air. Air contains about 21% by volume of oxygen. Oxygen is essential for combustion to occur.

Which of the following compounds produce $N _2$ on strong heating?

  1. $NaNO _2$

  2. $NaNO _3$

  3. $NH _4NO _2$

  4. $AgNO _3$


Correct Option: A
Explanation:

The thermal decomposition of sodium nitrite to produce sodium oxide(III), nitrogen and oxygen. This reaction takes place at a temperature of $700-900°C.$

$4NaN{ O } _{ 2 }→2{ Na } _{ 2 }O+2{ N } _{ 2 }+3{ O } _{ 2 }$