Kinetic Theory of Gases Assumptions Questions

Gas behaviour is investigated by considering either the small-scale activity of particular molecules or the large-scale movement of the gas. The large-scale action of the gas may be efficiently analysed and quantified; however, analysing the activity of the gas molecules needs a theoretical model. This theoretical model is called the kinetic theory of gases. It was established in the nineteenth century by physicists Rudolph, James Clerk Maxwell, and Clausius to describe the behaviour of gases. According to the theory, gas is composed of tiny, hard spheres interacting with one another and the wall’s surface. The spheres describe gas molecules and act by Newton’s 17th-century motion laws. It explains how molecules affect gas characteristics such as pressure and temperature. It also helps in understanding why gases obey Boyle’s law.

At low temperatures, volume (V), temperature (T) and pressure (P) of gases follow the below equation:

PV = nRT

Where,

R = Gas constant (8.314 JK^-1mol^-1)

n = Number of moles in the gas

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Kinetic Theory of Gases Assumptions

Important Questions with Answers

1. What are the assumptions of the kinetic theory of gases?

Below are the assumptions of gas kinetic theory:

• All gases are constructed up of molecules that constantly move in random paths.
• The laws of motion apply to all molecules in a given gas sample.
• The spacing between the molecules is substantially higher than their size.
• When a gas sample is stored in a container, the model molecules exert no force on the container walls during the collision.
• All collisions between molecules, as well as collisions between molecules and the walls, are expected to be elastic.
• The time delay between two molecules and between a molecule and the wall is thought to be relatively short.
• If a gas sample is left for a long time, it will eventually reach a steady state. The density and distribution of molecules do not depend on distance, position, and time.

2. What are the postulates of the kinetic theory of gases?

The following are the postulates of the kinetic theory of gases:

• The large space between the molecules produces continuous motion.
• The space-volume-to-molecule ratio is always negligible.
• The free mobility of molecules produces a perfectly elastic collision.
• Molecules exert pressure on the container’s walls.
• Because of their random mobility, the molecules contain kinetic energy. The average kinetic energy of these molecules, however, varies with temperature.
• At average pressure and temperature, there is no attraction between molecules. When the temperature and pressure decrease, the force of attraction between the molecules increases.

3. Which assumptions of the kinetic theory of gases are incorrect?

Van der Waal pointed out that the following two assumptions in kinetic theory are incorrect:

• If the pressure is low, this assumption is almost correct.
• The molecules have no attraction to each other.

4. Who created the kinetic theory of gases?

To describe the behaviour of gases, scientists Clausius, Rudolph, and James Clerk Maxwell created the kinetic theory of gases in the nineteenth century.

5. What are the three primary components of the kinetic theory of gases?

The three most significant components of the gas kinetic theory are:

• When molecules collide, no energy is collected or released.
• These molecules move in a straight path all the time.
• The area filled by gas molecules in a container is negligible.

6. What is the kinetic theory of gases?

Gas behaviour is investigated by considering either the small-scale activity of particular molecules or the large-scale movement of the gas. The large-scale action of the gas may be efficiently analysed and quantified; however, analysing the activity of the gas molecules needs a theoretical model. This theoretical model is called the kinetic theory of gases. According to the theory, gas is composed of tiny, hard spheres interacting with one another and the wall’s surface. The spheres describe gas molecules and act by Newton’s 17th-century motion laws. It explains how molecules affect gas characteristics such as temperature and pressure. It also helps in understanding why gases obey Boyle’s law.

At low temperatures, volume (V), temperature (T), and pressure (P) of gases follow the equation:

PV = nRT

Where, n = Number of moles in the gas and R = Gas constant ( 8.314 JK^-1mol^-1 )

7. The model of the kinetic theory of gases was established in the 19th century by physicists Rudolph, James Clerk Maxwell, and Clausius.

1. True
2. False

Answer: a. True

Explanation: To explain the behaviour of gases, scientists Clausius, Rudolph, and James Clerk Maxwell created the kinetic theory of gases in the nineteenth century.

8. Which condition is necessary for most gases to behave nearly ideally?

1. Low temperature and low pressure
2. High temperature and low pressure
3. Constant temperature and low pressure
4. None of the above

Answer: b. High temperature and low pressure

Explanation: Gases are most ideal at a high temperature and low pressure.

9. Do all gases have the same kinetic energy at the same temperature?

The average kinetic energy of gas particles is proportional to the absolute temperature of the gas, and all gases at the same temperature have the same average kinetic energy.

10. Why are gases highly compressible?

The atoms that comprise the liquid or solid are extremely close. Because there is no room between particular particles, they cannot pack together. Gases are highly compressible because most of their volume comprises large quantities of empty space between the gas particles.

Practice Questions

1. What happens if the kinetic energy of a gas is lowered?
2. How does the kinetic theory explain Boyle’s Law?
3. Does kinetic energy change with volume?
4. Why does temperature depend on kinetic energy?
5. Which phase of matter has the lowest kinetic energy?

To learn more about the kinetic theory of gases, watch the video below.

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