chemistry

Class 11 Chemistry States of Matter Gases Important mcqs for Exams

Class 11 Chemistry States of Matter Gases !!!

Important multiple choose questions:

At absolute zero , molecules of hydrogen gas has 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 gaseous state.

All types of molecular motions stops at this temperature and molecules have no kinetic energy.


An ideal gas can never be liquefied b/c:

1.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 liquid state.


Gases are less dense and highly compressible due to:

1.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 mass of an ideal gas, its volume can be kept constant by:

1.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 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 ideal gas at STP has the same volume of 22.4 dm3

2.Celsius and Fahrenheit temperature coincides at -400

3.S.I unit for 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: 1.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 occur due to :

1.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 occur due to large empty spaces among the molecules which are in constant random motion.


As compared to the lighter gases, heavier gas molecules have :

1.Higher average kinetic energy

2.Higher rates of diffusion

3.Lower rates of diffusion

4.Higher vapor pressures

Answer ) Lower rates of diffusion

Brief Explanation :

 At same temperature & pressure , heavier gas molecules have Lower velocity than lighter gas molecules.

As rate of diffusion is directly proportional to velocity , hence heavier gas molecules have lower rate of diffusion than the lighter gas molecules at same temperature and pressure.

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