Physics

Thermodynamics and Gas Laws

616 Questions

Thermodynamics and gas laws questions test the understanding of ideal gas behavior, work done during thermodynamic processes, and specific heat ratios. Key areas include isothermal, adiabatic, and isobaric expansions along with real gas deviations. These mathematical physics concepts are standard in engineering and general science competitive exams.

Ideal gas equationIsothermal and adiabatic processesThermodynamic workGas kinetic theoryReal gas behavior

Thermodynamics and Gas Laws Questions

Multiple choice

Boyle's law is applicable at ________.

  1. constant pressure

  2. constant temperature

  3. constant temperature and pressure

  4. variable temperature

  5. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Boyle's Law states that for a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional. Therefore, temperature must be constant.

Multiple choice

Which of the following is not an assumption of kinetic theory of gases?

  1. The actual volume of the gaseous molecules is negligible as compared to the total volume of the gas.

  2. The critical temperature is the measure of the kinetic energy of the molecule.

  3. The effect of gravity on motion of molecules is negligible.

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Given statement regarding the Kinetic Theory of gases is incorrect because it is not the critical temperature but only temperature which is the measure of the kinetic energy of the molecules. 

Multiple choice

Which of the following is not a property of a gas?

  1. Definite shape & volume

  2. Expansibility

  3. Diffusibility

  4. Low density
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Gases do not posses any definite shape or volume. They completely fill all the space available to them. The tendency of a gas to fill the available volume within a container is the result of the freedom that gas particles have to move everywhere in the available space. As a result the molecules of gas are in a continuous motion and are associated with high velocity and therefore high kinetic energy.

Multiple choice

PV = k = constant, is a mathematical expression of

  1. Charle's Law

  2. Avagadro's Law

  3. Graham's Law of diffusion

  4. Boyle's Law
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Robert Boyle proposed this law , giving the relationship between pressure and volume of given mass of a gas at constant temperature. This law states that volume (V) of a given mass of gas is inversely proportional to the pressure (P) at constant temperature. Mathematically it can be expressed as, or PV = k = constant.  At a given temperature, when the pressure of the gas is changed from P1 to P2 the relation becomes P1 V1 = P2 V2 = constant where, V2 is the new volume of the gas. The product of volume and pressure for a given mass of a gas at constant temperature is constant.

Multiple choice

Gases are formed when

  1. the energy of a system increases & breaks the rigid structure of the solid state

  2. the energy in the system exceeds all of the attractive forces between molecules

  3. the attractive forces between individual molecules are greater than the energy causing them to move apart

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Gases are formed when the energy in the system exceeds all of the attractive forces between molecules. Thus gas molecules have little interaction with each other beyond occasionally bumping into one another. In the gas state, molecules move quickly and are free to move in any direction, spreading out long distances. As the temperature of the gas increases, the amount of movement of individual molecules increases. Gases expand to fill their containers and have low density.

Multiple choice

Which of the following is not true for ideal gas?

  1. It obeys Boyle's Law

  2. It obeys Van Der Wall's equation

  3. It obeys Charle's Law

  4. It obeys perfect gas equation
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Ideal gas does not obey Van Der Wall's equation. It is obeyed by real gases. A real gas, does not obey the general gas equation and other gas laws at all conditions of temperature and pressure.

Multiple choice

The temperature above which further liquefication of gas is not possible by applying pressure is called

  1. critical pressure

  2. critical temperature

  3. critical volume

  4. critical constants
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

 It may be defined as the temperature above which a gas cannot be liquefied by application of pressure. A gas will remain as gas above critical temperature and in order to liquefy it by compression, it has to be cooled to its critical temperature. Critical temperature is denoted by Tc.

Multiple choice

Which of the following postulates is wrong regarding the Kinetic Theory of gases?

  1. It is based on wave nature of matter

  2. Rapid motion & collision of molecules

  3. Perfectly elastic molecular collisions

  4. Negligible forces between the molecules
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In order to explain the observed behaviour of gases, a model was proposed based on the molecular and kinetic concept of gas molecules. This model takes into account the particulate nature of matter and the constant movement of particles.

Multiple choice

Directions: For the Assertion (A) and Reason (R) below, choose the correct alternative from the following. Assertion: As the pressure increases, the volume decreases if the temperature is constant. Reason: When temperature is constant, pressure and volume are inversely proportional to each other.

  1. Both A and R are true and R is the correct explanation of A.

  2. Both A and R are true but R is not the correct explanation of A.

  3. A is true but R is false.

  4. A is false but R is true.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Both A and R are true and because of the reason the assertion is true. Hence, option (1) is correct.

Multiple choice

In gases, particles vibrate _________.

  1. about their mean position

  2. about a vertical axis

  3. about a horizontal axis

  4. in any direction
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The particles of gas, either atoms or molecules, have too much energy to remain attached to one other. The move by translation, rotation and vibration, but in this case the translational motion is the most important. The particles are on average very far apart and collide incessantly many times a second. Because of the distance between them it is assumed that the forces of attraction between the particles are negligible.

Multiple choice

In gases, particles vibrate _________.

  1. about their mean position

  2. about a vertical axis

  3. about a horizontal axis

  4. in any direction
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The particles of gas, either atoms or molecules, have too much energy to remain attached to one other. The move by translation, rotation and vibration, but in this case the translational motion is the most important. The particles are on averagevery far apart and collide incessantly many times a second. Because of the distance between them it is assumed that theforces of attraction between the particles are negligible.