Kinetic Molecular Theory

Kinetic Molecular Theory MDCAT MCQs with answers

19 past paper MCQs on Kinetic Molecular Theory, from the Gases unit of MDCAT Chemistry. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

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1.The process of heat flow between hotter and colder gases continues until all the molecules have equal: (MDCAT 2022)

  1. average translational kinetic energy
  2. average rotational kinetic energy
  3. average translational potential energy
  4. average vibrational kinetic energy
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Correct answer: (a) average translational kinetic energy

Temperature measures the average translational kinetic energy, and heat flows until the two gases share it equally.

2.The process of heat flow between hotter and colder bodies stops when their molecules have equal: (MDCAT 2023)

  1. average translational kinetic energy
  2. average rotational kinetic energy
  3. average translational potential energy
  4. average vibrational kinetic energy
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Correct answer: (a) average translational kinetic energy

Temperature is a measure of the average translational kinetic energy, and heat flows until the two are equal.

3.The intermolecular forces between the molecules of an ideal gas are: (MDCAT 2024)

  1. strong
  2. moderate
  3. weak
  4. absent
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Correct answer: (d) absent

The kinetic theory of an ideal gas assumes no attraction between the molecules at all.

4.Which of the following is NOT a postulate of kinetic molecular theory of gases? (KMU MDCAT 2025)

  1. Gas molecules undergo elastic collision
  2. Gas molecules are in continuous random motion
  3. Gas molecules do not exert pressure when molecules collide with wall of container
  4. Gas molecules are far away from each other
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Correct answer: (c) Gas molecules do not exert pressure when molecules collide with wall of container

The theory says pressure is precisely the result of those collisions with the walls.

5.Which of the following relationship is correct for kinetic energy of gases? (NUMS MDCAT 2025)

  1. K.E = 2RT/3NA
  2. K.E = 3RT/2NA
  3. K.E = 2mNT/2R
  4. K.E = 2NA/3RT
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Correct answer: (b) K.E = 3RT/2NA

The mean translational energy of one molecule is $\tfrac32RT/N_A$.

6.The fourth state of matter is: (NUMS MDCAT 2025)

  1. Solid
  2. Liquid
  3. Gaseous liquid
  4. Plasma
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Correct answer: (d) Plasma

A gas heated until its atoms ionize becomes plasma, the fourth state of matter.

7.According to the Kinetic molecular theory, the kinetic energy of gas molecules increases when they are (SZABMU MDCAT 2025)

  1. melted from solid to liquid state
  2. mixed with other molecules at lower temperature
  3. frozen into solids
  4. condensed into liquids
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Correct answer: (a) melted from solid to liquid state

Melting raises the temperature at which the particles move, so their kinetic energy rises.

8.Which statement applies to both ideal and real gases (SZABMU MDCAT 2025)

  1. collision between molecules are elastic
  2. molecules are in constant random motion
  3. molecules attract each other
  4. molecules have zero size
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Correct answer: (b) molecules are in constant random motion

Continuous random motion is common to both; only the ideal gas has point molecules that do not attract.

9.The relationship between absolute temperature and velocities of gas molecules is given by: (NUMS MDCAT 2024)

  1. Crms = sqrt(3RT/M)
  2. PV = nRT
  3. V = sqrt(2Ek/m)
  4. PV = 1/3mNc2
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Correct answer: (a) Crms = sqrt(3RT/M)

The root mean square speed is $\sqrt{3RT/M}$.

10.The process of heat flow between hotter and colder gases remains continued until all the molecules have equal (UHS MDCAT 2023)

  1. Average translational kinetic energy
  2. Average rotational kinetic energy
  3. Average translational potential energy
  4. Average vibrational kinetic energy
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Correct answer: (a) Average translational kinetic energy

Temperature is a measure of the mean translational kinetic energy, so heat flows until those are equal.

11.Air is a mixture of gases. The molecules of air do notsettle down due to: (SZABMU MDCAT 2023)

  1. Different molar mass
  2. Non polar nature of gases
  3. Presence of dust particles in air
  4. Elastic collision of gas molecules
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Correct answer: (d) Elastic collision of gas molecules

The molecules keep their energy through collisions, so they stay in ceaseless motion and never settle.

12.Collision shown by gases involve the following: (SZABMU MDCAT 2023)

  1. No energy change
  2. No pressure change
  3. Small energy change
  4. Large energy change
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Correct answer: (a) No energy change

Gas collisions are perfectly elastic, so no kinetic energy is lost in them.

13.The idea that molecules in gases are in constant movement is called: (NUMS MDCAT 2023)

  1. Kinetic theory of gases
  2. Crystal field theory
  3. Molecular orbital theory
  4. Transition state theory
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Correct answer: (a) Kinetic theory of gases

That is the kinetic molecular theory of gases.

14.According to the kinetic molecular theory, collisions between the gas molecues: (PMC MDCAT 2022)

  1. Are elastic
  2. Are non-elastic
  3. Increase energy
  4. Decrease energy
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Correct answer: (a) Are elastic

Collisions between gas molecules are perfectly elastic, so no kinetic energy is lost.

15.Spreading of scent in the air is due to: (PMC MDCAT 2022)

  1. Diffusion of gas molecules
  2. Effusion of gas molecules
  3. Volume of gas
  4. Temperatue of gas
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Correct answer: (a) Diffusion of gas molecules

The molecules of the scent move at random and spread through the air, which is diffusion.

16.Gases can easily mix with each other to form a uniform mixture, this property Is called: (PMC MDCAT 2022)

  1. Effusion
  2. Homogenous Mixing
  3. Diffusion
  4. Heterogenous mixing
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Correct answer: (c) Diffusion

The spontaneous intermingling of gases is diffusion.

17.Kinetic Energy is the sum of ______. (PMC Practice 2021)

  1. Rotational & Vibrational
  2. Translational & Rotational
  3. Rotational, Vibrational, and Translation
  4. All of these are correct
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Correct answer: (c) Rotational, Vibrational, and Translation

A molecule can move bodily, spin and vibrate, and all three carry kinetic energy.

18.All the collisions between the particles of gases are elastic in nature. What is meant by “Elastic Collisions”? (UHS MDCAT 2019)

  1. No change in the total kinetic energy
  2. The velocity of the molecules changes
  3. No change in potential energy during the collisions
  4. No change in mass during the collisions
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Correct answer: (a) No change in the total kinetic energy

An elastic collision is one in which the total kinetic energy is unchanged.

19.Gas is enclosed in a container of 20 cm3 with the moving piston. According to kinetic theory of gases, what will be the effect on freely moving molecules of the gas if temperature is increased from 20 C to 100 C? (UHS MDCAT 2018)

  1. Pressure will become one half
  2. Volume will be increased
  3. Temperature has no effect on freely moving molecules
  4. Colliding capability of molecule will become lower
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Correct answer: (b) Volume will be increased

The molecules move faster and strike the piston harder, so at constant pressure the gas expands.

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