Kinetic Theory (VSAQs)

Physics-1 | 14. Kinetic Theory – VSAQs:
Welcome to VSAQs in Chapter 14: Kinetic Theory. This page includes the key FAQs for Very Short Answer Questions. Answers are provided in simple English and follow the exam format. This helps you focus on essential points and aim for top marks in your final exams.

VSAQ-1 : When does a real gas behave like an ideal gas?

  1. Low Pressure: Real gases tend to behave like ideal gases at low pressures, where the individual gas molecules are relatively far apart, and the intermolecular forces are negligible.
  2. High Temperature: Real gases approach ideal behavior at high temperatures, where the kinetic energy of the gas molecules is sufficient to overcome intermolecular forces, resulting in minimal deviation from ideal gas behavior.
  3. Large Volume: At large volumes, the effect of molecular size becomes less significant, and real gases behave more closely to ideal gases.

VSAQ-2 : State Boyle’s Law and Charles Law.

Boyle’s Law: Boyle’s Law states that at constant temperature, the volume of a fixed amount of gas is inversely proportional to its pressure. In simpler terms, when the pressure on a gas increases, its volume decreases, and when the pressure decreases, the volume increases, provided the temperature remains constant.

Charles’s Law: Charles’s Law states that at constant pressure, the volume of a given amount of gas is directly proportional to its absolute temperature. In other words, as the temperature of a gas increases, its volume also increases, and as the temperature decreases, the volume decreases, as long as the pressure remains constant.

VSAQ-3 : Define mean free path.

The mean free path is the average distance that a molecule or particle travels between consecutive collisions with other molecules or particles within a gas. It quantifies the typical distance a particle can move before encountering another particle. The concept of mean free path is essential for comprehending gas behavior and is particularly relevant in the fields of physics and engineering, where it aids in the study of gas dynamics and particle interactions.

VSAQ-4 : State Dalton’s Law of partial pressures.

Dalton’s law of partial pressures asserts that the total pressure exerted by a mixture of non-reacting gases is equal to the sum of the partial pressures of each individual gas within the mixture. In simpler terms, the pressure contributed by each gas in the mixture is independent of the presence of other gases. This law serves as a fundamental principle for comprehending the behavior of gas mixtures and finds extensive application in various contexts, including determining gas composition in mixtures and calculating specific gas pressures within a system.

VSAQ-5 : State the law of equipartition of energy.

The law of equipartition of energy specifies that in a state of thermal equilibrium, the total energy of a system is evenly distributed among all its accessible degrees of freedom. For a molecule within a system, each degree of freedom contributes an average energy of 1/2 kT, where k represents the Boltzmann constant and T denotes the temperature on the absolute scale. This law holds significance in statistical mechanics and thermodynamics as it aids in comprehending how energy is distributed across various modes of motion for particles within a system at a given temperature.

VSAQ-6 : What are the units and dimensions of a specific gas constant?

  1. Units: Joules per mole-kelvin (J/mol·K) in SI.
  2. Dimensions: [M L^2 T^-2 K^-1 mol^-1], representing energy per mole per temperature.

VSAQ-7 : Define absorptive power of a body. What is the absorptive power of a perfect black body?

  1. Absorptive Power: It’s a measure of a body’s ability to absorb incoming radiation.
  2. Perfect Black Body: It has an absorptive power of 1, absorbing all incident radiation and not reflecting or transmitting any.

VSAQ-8 : Pressure of an ideal gas in container is independent of shape of the container-explain

Pressure in an ideal gas is independent of the shape of the container because it’s determined by the kinetic energy and number of gas molecules colliding with the container walls. Gas molecules fill the space, exerting equal pressure on all inner surfaces, making shape irrelevant.

VSAQ-9 : What is the expression between the pressure and kinetic energy of a gas molecules?

The expression between the pressure (P) and kinetic energy of gas molecules is described by the ideal gas law: PV = 2/3 NkT. Here, P represents pressure, V is volume, N is the number of gas molecules, k is the Boltzmann constant, and T is the absolute temperature. This equation illustrates how pressure is related to the kinetic energy of gas molecules in an ideal gas.

VSAQ-10 : The absolute temperature of a gas is increased 3 times. What will be the increase in rms velocity of the gas molecule?

When the absolute temperature of a gas is increased three times, the root mean square (rms) velocity of the gas molecules will increase by the square root of 3 (√3) times. This relationship is described by the ideal gas law, which states that the rms velocity of gas molecules is directly proportional to the square root of the absolute temperature.