Chemistry · Physics

Gases and Gas Laws

298 Questions

The study of gases and gas laws involves understanding the relationships between pressure, volume, and temperature of gases. This topic is essential for chemistry and physics sections in many competitive exams. Practice these questions to master concepts like the ideal gas law, partial pressure, and molecular properties.

Ideal gas law calculationsGas volume and pressureStoichiometry of gasesDensity of gasesBoltzmann constant applicationsThermal speed of sound

Gases and Gas Laws Questions

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

Ethane burning in oxygen to give carbon dioxide and steam. The volume ratio of reactants to products is ______________.

  1. 2 : 6 : 4 : 3

  2. 2 : 7 : 2 : 5

  3. 3 : 4 : 4 : 6

  4. 2 : 7 : 4 : 6
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The equation for the combustion reaction of ethane can be written as :
$2C _{2}H _{6} + 7O _{2} \rightarrow 4CO _{2} + 6H _{2}O$
Therefore the volume ratio of reactants and products $= 2 : 7 : 4 : 6$

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

Four one litre flasks are separately filled with gases $O _2, F _2, CH _4$ and $CO _2$ under same conditions. 


The ratio of the number of molecules in these gases are:

  1. $2 : 2 : 4 : 3$
  2. $1 : 1 : 1 : 1$
  3. $1 : 2 : 3 : 4$
  4. $2 : 2 : 3 : 4$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Avogadro's law: It states that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

$\\ n _{1} : n _{2} : n _{3} : n _{4} = \cfrac{PV}{RT} : \cfrac{PV}{RT} : \cfrac{PV}{RT} : \cfrac{PV}{RT} = 1 : 1 : 1 : 1 $

So, the ratio of no. of molecules $= 1: 1: 1: 1$

The correct option is $B.$
Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

One gram molecule of any gas at $NTP$ occupies $22.4\ L$. This fact was derived from:

  1. Dalton's theory

  2. Avogardro's hypothesis

  3. Berzelius hypothesis

  4. Law of gaseous volume
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

According to Avogadro's law, 1 mole of every gas occupies 22.4L at $NTP$.

From ideal gas equation,
$PV=nRT$. . . . . . .(1)
At $NTP$,
$T=273K$
$P=1atm$
$n=1$
$R=0.0821atm L/K mol$
from equation (1),
$V=\dfrac{nRT}{P}$
$V=\dfrac{1\times 0.0821\times 273}{1}=22.4L$
The correct option is B.

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

A vessel contains N molecules of oxygen at a certain temperature and pressure. How many molecules of sulphur dioxide can the vessel accommodate at the same temperature and pressure.

  1. N

  2. 2N

  3. N/2

  4. 4N
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

As both have same volume and according to avagadro's law, equal volume of gases contains equal molecules so sulphur dioxide contains N molecules.

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

A vessel contains X number of molecules of hydrogen gas at a certain temperature and pressure. Under the same conditions of temperature and pressure, how many molecules of nitrogen gas would be present in the same vessel?

  1. 2X

  2. X

  3. 0.5X

  4. 3X
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Avogadro's law states that, "equal volumes of all gases, at the same temperature and pressure, have the same number of molecules" so same volume of nitrogen will have X number of molecules.

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

If $1$ L of $O _2$ at $15^oC$ and $750$ mm pressure contains $\text N$ molecules, the number of molecules in $2$ L of $SO _2$ under the same conditions of temperature and pressure will be :

  1. $\dfrac {\text N}{2}$
  2. $\text N$
  3. $2\text N$
  4. $4\text N$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Under similar conditions of temperature and pressure, equal volume of gas contains equal number of molecules.
$\therefore 1\ L=N$ molecules
$2\ L=2\ N$ molecules

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

Four 1-1 litre flasks are separately filled with the gases $H _2,\, He,\, O _2$ and ozone. The ratio of total number of atoms of these gases present in different flask would be : 

  1. 1 : 1 : 1 : 1

  2. 1 : 2 : 2 : 3

  3. 2 : 1 : 2 : 3

  4. 3 : 2 : 2 : 1
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to Avogadro's law, all gases at same temperature and pressure will contain same number of molecules. Hence, number of molecules of all gases will be same bt ration of atoms of each gases will $2:1:2:3$.

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

Hydrogen, oxygen and carbon dioxide are taken in containers of $2 l$ volume each. Compare the ratio of the number of molecules of the three gases respectively, under same conditions of temperature and pressure.

  1. 1:8:22

  2. 1:1:1

  3. 1:16:44

  4. 1:8:44
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Using ideal gas law: PV =nRT

n = $\dfrac{V}{RT}$
here P, R and T= Constant, V = 2l
hence number of moles also equal  
the ration of moles equal to 1:1:1
 answer is B

Multiple choice chemistry atoms and molecules avogadro hypothesis avogadro's law avogadro law

A mixture of helium and argon contains 3 moles of $He$ for every 2 moles of $Ar$. The partial pressure of argon in the mixture is

  1. two thirds the total pressure

  2. one third the total pressure

  3. three fifths the total pressure

  4. two fifths the total pressure
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The partial pressure of any gas is the product of mole fraction and total pressure


$P _{Ar}=\dfrac{2}{2+3}.P _{total}$

Multiple choice chemistry atoms and molecules avogadro hypothesis avogadro's law avogadro law

A sample of gas has a volume of 0.2 litres measured at 1 atm pressure and $0^oC$. At the same pressure, at $273^oC$, its volume will become:

  1. 0.1 litre

  2. 0.4 litre

  3. 0.8 litre

  4. 0.6 litre
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

According to Charles's law


$\dfrac{V _1}{T _1}=\dfrac{V _2}{T _2}$

$\dfrac{0.2}{273}=\dfrac{V}{546}$

$V=0.4\ litres$

Multiple choice chemistry atoms and molecules avogadro hypothesis avogadro's law avogadro law

A gas is initially at $1$ atm pressure. To compress it to $1/4$ th of its initial volume, pressure to be applied is:

  1. $1$ atm
  2. $2$ atm
  3. $4$ atm
  4. $1/4$ atm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to boyle's law,


$P _1V _1=P _2V _2$

$\Rightarrow 1.V=\frac{V}{4}.P _2$

$\Rightarrow P _2=4\ atm$

Hence, the correct option is $C$

Multiple choice chemistry quantitative chemistry avogadro hypothesis avogadro's law avogadro law

At room temperature and pressure, two flasks of equal volumes are filled with $H _2$ and $SO _2$ separately. Particles which are equal in number, in the two flasks are:

  1. atoms

  2. electrons

  3. molecules

  4. neutrons
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

At a given volume at constant temperature and pressure, two gases have equal no. of moles 

hence, the no. of molecules will be same in both flasks.