Class 11 Chemistry States of Matter Gases
Important multiple choice questions:
At absolute zero, molecules of hydrogen gas have energy:
- 1. Translational only
2. Rotational only
3. Vibrational only
4. None of these
Answer ) None of these
Brief Explanation :
Absolute zero is the lowest possible temperature at which no gas can exist in a gaseous state.
All types of molecular motions stop at this temperature and molecules have no kinetic energy.
An ideal gas can never be liquefied b/c:
- Molecules are smaller
2. Molecules are non-polar
3. Molecules are non-interacting
4. Solidifies directly
Answer ) Molecules are non-interacting
Brief Explanation :
An ideal gas can never be liquefied because its molecules are non-interacting i.e. have no attractive forces to change them into a liquid state.
Gases are less dense and highly compressible due to:
- Small size of molecules
2.No attraction among molecules
3. High kinetic energy of molecules
4. Larger empty spaces among molecules
Answer ) Larger empty spaces among molecules
Brief Explanation :
Gases are separated by large empty spaces & thus gases are less dense and highly compressible.
A hyperbolic plot of P versus V for a gas at constant temperature means that :

Answer ) Both 2 & 3

Avogadro’s law states that for different gases:




Combined gas law states that:


The value of Universal gas constant R in S.I unit is:
1.1.987 cal.k-1.mol-1
2.8.314 J.k-1.mol-1
3.0.0821 L.atm.k-1.mol-1
4.All of these
Answer ) 8.314 J.K-1 mol-1
Brief Explanation :
The value of universal gas constant in S.I units is , which can be calculated by taking:
n=1mol : P = 1atm = 101325 Nm-2
V= 22.4 dm3= 0.0224 m3
Now we have that R= P x V / n x T
R= 0.0224 m3 x 101325 Nm-2 /1mol x 273 K
R = 8.314 Nm2 K-1 . mol-1
or R = 8.314 J K-1 . mol-1
When gas is compressed , its mass:
1.Increase
2.Decreases
3.Disappears
4.Remains Constant
Answer ) Remains Constant
Brief Explanation :
When a gas is compressed , the molecules come closer & inter- molecular spaces decreases but the mass remains the same.
At the same temperature and pressure, different gases have the same:
1.Average molecular speeds
2.Average Kinetic energy
3.Molecular masses
4.Density
Answer ) Average Kinetic energy

By increasing the mass of an ideal gas, its volume can be kept constant by:
- Lowering T & P
2. Raising T & P
3. Raising P & Lowering T
4. Lowering T & applying P
Answer ) Raising P & Lowering T
Brief Explanation :
When the mass of an ideal gas is increased, its volume can be kept constant by applying pressure & decreasing temperature.
It will bring the gas molecules closer together to keep the volume constant when mass is increased.
Pick up the correct statement:
1.1 mole of an ideal gas at STP has the same volume of 22.4 dm3
2. Celsius and Fahrenheit’s temperature coincides at -400
3.S.I unit for the pressure of a gas is Pascal
4. All of these
Answer ) All of these
Brief Explanation :
All the given statements are correct.
A process that clearly suggests that matter is made up of tiny particles, which are in constant random motion, is:
- Condensation
2. Combustion
3. Conduction
4. Diffusion
Answer ) Diffusion
Brief Explanation :
Diffusion provides evidence that matter consists of tiny particles which are in constant random motion b/c diffusion can occur when the particles are separated by empty spaces.
Diffusion of gases occurs due to :
- Empty spaces among molecules
2. Collisions among molecules
3. Attraction among molecules
4. None of these
Answer ) Empty spaces among molecules
Brief Explanation :
Diffusion of gases occurs due to large empty spaces among the molecules which are in constant random motion.
As compared to the lighter gases, heavier gas molecules have :
- Higher average kinetic energy
2. Higher rates of diffusion
3. Lower rates of diffusion
4. Higher vapour pressures
Answer ) Lower rates of diffusion
Brief Explanation :
At the same temperature & pressure, heavier gas molecules have Lower velocity than lighter gas molecules.
As the rate of diffusion is directly proportional to velocity, hence heavier gas molecules have a lower rate of diffusion than the lighter gas molecules at the same temperature and pressure.
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