Free Thermodynamics MCQs with Answers
714 Thermodynamics MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Thermal equilibrium and heat explain how temperature and energy transfer are related, while molar specific heats describe the heat required by a gas at constant volume or constant pressure. The first law connects heat supplied, work done and change in internal energy, with sign conventions kept distinct from temperature changes.
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681. A heat engine:
- A. Converts heat input to an equivalent amount of work
- B. Converts work to an equivalent amount of heat
- C. Takes heat in, does work, and loses energy as heat
- D. Uses positive work done on the system to transfer heat from a low temperature reservoir to a high temperature reservoir
Explanation: A heat engine is a device that operates on the principle of converting heat energy into mechanical work, often by using a working…
Correct answer: Converts heat input to an equivalent amount of work- A. The heat capacity of working substances
- B. Only the temperature of two reservoirs
- C. The reservoir temperature and the heat capacity of working substance
- D. The reservoir temperature and the volume chnage during heat absorption
Explanation: The Carnot engine is a theoretical thermodynamic cycle proposed by Nicolas Léonard Sadi Carnot in 1824.
Correct answer: Only the temperature of two reservoirs- A. The density increases
- B. The latent heat increases
- C. The molecule vibrates more rapidly
- D. The melting point increases
Explanation: The changes that take place when a solid is heated (increase in temperature) are as follows:On increasing the temperature of solids, the…
Correct answer: The molecule vibrates more rapidly- A. Zero
- B. Positive
- C. Negative
- D. None of the above
Explanation: The Carnot Cycle is a thermodynamic cycle that consists of four subsequent reversible processes: isothermal expansion, adiabatic…
Correct answer: Zero- A. Enthalpy is constant
- B. Temperature is constant
- C. Pressure is constant
- D. No heat enters or leaves the system
Explanation: An isothermal change refers to a process in which the temperature of a system remains constant throughout the process.
Correct answer: Temperature is constant- A. Specific heat
- B. Molar specific heat
- C. Heat capacity
- D. Heat of vaporization
Explanation: The amount of heat energy required to raise the temperature of a body through 1 K (or 1 °C) is called:Heat capacity
Correct answer: Heat capacity- A. 775.00 K
- B. 774.85 K
- C. 228.85 K
- D. 228.70 K
Explanation: To convert from Celsius (C) to thermodynamic temperature, also known as Kelvin (K), you can use the formula:Kelvin (K) = Celsius (C) +…
Correct answer: 775.00 K688. The statement that heat cannot spontaneously flow from a colder to a hotter body is a result of:
- A. Henry's law
- B. The first law of thermodynamics
- C. The second law of thermodynamics
- D. The third law of thermodynamics
Explanation: 2nd law of thermodynamics expresses a fundamental and simple truth about the universe, it states that heat cannot flow from colder body to…
Correct answer: The second law of thermodynamics- A. 775.00 K
- B. 774.85 K
- C. 228.85 K
- D. 228.70 K
Explanation: Thermodynamic temperature, by contrast, is an absolute measure of the average total internal energy of an object or objects-namely its…
Correct answer: 775.00 K- A. Molecules do not exert any force on each other
- B. The size of molecules is much larger than the separation between the molecules
- C. A finite volume of gas consists of a very small number of molecules
- D. The gas molecules are not in random motion
Explanation: A postulate of the kinetic theory of gases is that molecules exert no force on one another except during the instant of collision, which…
Correct answer: Molecules do not exert any force on each other- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: Root mean square speed follows from PV = (1/3)Nm<v^2>, giving v_rms = sqrt(3PV/Nm), equivalently sqrt(3kT/m) for one molecule or…
Correct answer: Option A- A. Collisions between gas molecules occur
- B. Collisions between gas molecules occur linearly
- C. Collisions must be elastic
- D. Collisions must be inelastic
Explanation: The kinetic theory assumes collisions between gas molecules are perfectly elastic, so kinetic energy is conserved in every collision.
Correct answer: Collisions must be elastic- A. 4 root mean square of oxygen
- B. ¼ root mean square of oxygen
- C. 1/16 root mean square of oxygen
- D. 1/6 root mean square of oxygen
Explanation: At the same temperature v_rms is inversely proportional to the square root of molecular mass, since v_rms = sqrt(3kT/m).
Correct answer: 4 root mean square of oxygen- A. Option A
- B. Option B
- C. Option C
- D. Option D
Explanation: Mean square speed is the average of the squares of the molecular speeds, <v^2> = (v1^2 + v2^2 + ...
Correct answer: Option B- A. N/a^2
- B. m/a^3
- C. Nm/a^3
- D. Na^3/m
Explanation: Density is total mass divided by total volume. N molecules of mass m each give a total mass of Nm, and a cube of side a has volume a^3, so…
Correct answer: Nm/a^3- A. n = NNA
- B. n = N/NA
- C. n = NA/N
- D. n = N + NA
Explanation: The number of moles is the number of molecules divided by Avogadro's number: n = N/NA.
Correct answer: n = N/NA- A. 496.38 K
- B. 438.96 K
- C. 0
- D. 496.38 oF
Explanation: A constant-volume gas thermometer gives T = T_triple x (P/P_triple), with the triple point of water at 273.16 K.
Correct answer: 496.38 K- A. Avogadro's constant
- B. Charles constant
- C. Newton's constant
- D. Boltzmann's constant
Explanation: The universal gas constant divided by Avogadro's number is the Boltzmann constant, k = R/NA = 1.38 x 10^-23 J/K.
Correct answer: Boltzmann's constant- A. Charles Law
- B. Avogadro's Law
- C. Newton's Constant
- D. Ideal Gas Law
Explanation: PV = nRT is the ideal gas law, which combines Boyle's law, Charles's law and Avogadro's law into a single equation of state.
Correct answer: Ideal Gas Law- A. 1 x 10³ Pa
- B. 2.5 x 10² Pa
- C. 1 x 10² Pa
- D. 2.7 x 10³ Pa
Explanation: Kinetic theory gives P = (1/3) x density x mean square speed. Substituting, P = (1/3) x 6 x 500 = 1000 Pa, which is 1 x 10^3 Pa.
Correct answer: 1 x 10³ Pa