# Thermodynamics -Multiple Choice Questions(MCQ)

• What is the basis for the first law of thermodynamics?

a) Conservation of energy
b) Conservation of mass

c) Conservation of momentum

d) Conservation of work

The conservation of energy is the foundation of the first law of thermodynamics, as explained. It deals with the labor performed and the heat energy added to or taken away from a system. In essence, it states that the energy that is supplied to a system is conserved

• Which of the following is not a statement of law of thermodynamics?

a) Energy can neither be created nor be destroy

b) The total energy of the universe remains constant

c) Enthalpy change depends only upon initial and final state

d) It is impossible to construct a perpetual motion machine.

• ΔU=0 denotes an isothermal process. False or True?

a) True
b) False

The only factor affecting internal energy is temperature. As a result, if ΔU=0, the process is isothermal or will have a constant temperature.

• Which of the following happens without a shift in internal energy?

a) Isochoric process
b) Isenthalpic process
d) Isenthalpic process

In a steady-state operation, internal energy remains constant.

An adiabatic process does not result in heat loss or gaining energy.
i) The isenthalpic process takes place at a constant enthalpy.
ii) When the pressure is constant, the isobaric process takes place.
iii) The volume of the isochoric process, also known as the isometric or isovolumetric process, remains constant.
iv) An isothermal process takes place at a constant temperature.
v) An isentropic process is a reversible, adiabatically occurring process with constant entropy.

• For a gas’s adiabatic compression

a) ∆U = W
b) ∆U =0
c) W=0
d) q ≠ 0

• What is thermodynamics?

a) Studying the relationship between heat and other forms of energy

b) chemical energy conversion

c) the relationship between mechanical energy and other forms of energy,

d) the conversion of mechanical energy to other forms of energy

The relationship between heat and other types of energy, such as mechanical, electrical, and chemical energy, is a focus of this branch of physical science.

• Which of the following is a thermodynamics branch?

a) Equilibrium thermodynamics
b) Classical thermodynamics
c) Chemical thermodynamics
d) All of the mentioned

Thermodynamics has the following branches:

1) Equilibrium thermodynamics
2) Classical thermodynamics
3) Chemical thermodynamics
4) Statistical mechanics or Statistical thermodynamics

• Thermodynamics is based on study of …… of the system.

a) microscopic properties

b) macroscopic properties

c) physical properties

• Which of the following characteristics is unaffected by the path change?

a) Work
b) Heat
c) change in enthalpy
d) both a and b

• Which of the following represents the thermochemical equation for standard heat of formation of methane?

a) C (g) + 4H (g) ⟶ CH4 (g)

b) C (diamond) + 4H (g) ⟶ CH4 (g)

c) C (diamond) + 2H2 (g) ⟶ CH4 (g)

d) C (graphite) + 2H2 (g) ⟶ CH4 (g)

• Thermodynamics is not concerned about______.

(a) energy changes involved in a chemical reaction.

(b) the extent to which a chemical reaction proceeds.

(c) the rate at which a reaction proceeds.

(d) the feasibility of a chemical reaction.

• Which of the following is false?

(a) ΔH = ΔE + PV at constant pressure
(b) Entropy is denoted by the thermodynamic symbol S.
(c) ΔH is negative for an endothermic process.
(d) ΔE is negative if the system produces more work than it absorbs in the form of heat.

• Which of the following types of balance is taken when multiple fluid streams enter or exit the control volume?

a) mass balance
b) energy balance
c) mass balance and energy balance
d) none of the above

Answer: The balance of mass and energy helps to take into account in this case.

• The temperature at which a system goes through a reversible isothermal process without transferring heat is

a) triple point of water
b) boiling point of water
c) absolute zero
d) none of the above

The temperature is zero and Q, the amount of heat supply has the smallest possible value of zero.

• Air-refrigeration cycle________________?

(a) has a very low efficiency

(b) is the most efficient refrigeration cycle

(c) needs a lot of air to achieve significant refrigeration

(d) Both B and C

• The following conditions must be met in order for a cycle to be reversible:

(a) Free expansion or friction-resisted expansion/compression should not occur

(b) The temperature of the hot source and the working substance should be the same when heat is being absorbed.

(c) The temperature of the cold source and the working substance should be the same when beat is being rejected.
d) all of above

• The formula S = qrev/T can be used to calculate the entropy change. Pick the appropriate answer from the list below when water freezes in a glass beaker.

(a) The system’s ∆S value drops while the environment’s ∆S value stays the same.

(b) ∆S (system) increases but ∆S (surroundings) decreases.

(c) While ∆S (system) declines, ∆S (environment) rises.

(d) ∆S (system) decreases and ∆S (surroundings) also decreases.

Answer: ∆S (system) decreases but ∆S (surroundings) increases

• After taking a bath during the hot summer, the body’s

a) internal energy decreases

b) internal energy increases

c) heat decreases

d) no change in internal energy and heat

Temperature decreases, So internal energy decreases.

• Which of the following laws was formulated by Nernst?

a) First law of thermodynamics
b) Second law of thermodynamics
c) Third law of thermodynamics
d) None of the above

Answer: (c) Third law of Thermodynamics

• Heat supplied to a system is

(a) Work done – Change in internal energy
(b) Work done + Change in internal energy
(c) Work done = Change in internal energy
(d) None

• The temperature at which all the gases become liquid is called:

(a) negative 273 K

(b) 0  °C

(c) Absolute zero

(d) 273 K

• Which of the following processes is reversible?

(a) Transfer of heat by conduction
(b) Transfer of heat by radiation
(c) Isothermal compression
(d) Electrical heating of a nichrome wire.

• Which of the aforementioned phenomena can be reversed?

(a) Water fall.
(b) Charging of a battery.
(c) Rusting of iron by chemical change.
(d) Production of heat by rubbing of hands.

• A gas is compressed isothermally to half its initial volume. The same gas is compressed separately through an adiabatic process until its volume is again reduced to half. Then –

(a) compressing the gas through an adiabatic process will require more work to be done

(b) compressing the gas isothermally or adiabatically will require the same amount of work

(c) which of the case (whether compression through isothermal or through the adiabatic process) requires more work will depend upon the atomicity of the gas

(d) compressing the gas isothermally will require more work to be done
Answer: (a) compressing the gas through an adiabatic process will require more work to be done

• A sink, the system where heat is rejected, is essential for converting heat into work. From which law the above inference follows?

(a) zeroth

(b) First

(c) Second

(d) Third

For heat to be converted into work, a sink—a system that rejects heat—is required. Otherwise, there won’t be a positive change in the universe’s entropy. which, by the second law of thermodynamics, is necessary.

• The difference between the specific heat at constant pressure and constant volume is caused by the fact that:

(a) molecular oscillations are more violent at constant pressure.
(b) additional work need to be done for allowing expansion of gas at constant pressure.
(c) there is more intermolecular attraction at constant pressure.
(d)None of the aforementioned.

Additional work need to be done for allowing expansion of gas at constant pressure.

• A refrigerator is a

(a) heat engine working in the backward direction

(b) air cooler

(c) an electric motor

(d) heat engine

Heat engine working in a backward direction Explanation: As we know, a heat engine is something that converts heat into mechanical work. Usually, a refrigerator is a device that is used to cool things. But according to the second law of thermodynamics, a refrigerator is a device that is used to turn mechanical work into heat. Therefore, we can say that a refrigerator is a heat engine that works in a backward direction.

• Which of the following statements made by Clausius is accurate?

(a) it is possible to build a device that can transfer heat from a cooler body to a hotter body without having any negative effects

(b) it is impossible to build a device that can transfer heat from a cooler body to a hotter body without having any negative effects

(c) it is impossible to build a device that can transfer heat from a hotter body to a cooler body without having any negative effects

(d) none of the above

To transfer heat from a cooler body to a hotter body, some work is expended.

• The product of an extensive and intensive variable is?

(a) Extensive
(b) Intensive
(c) Depends on temperature conditions
(d) Depends on pressure conditions

Since their product also depends on mass and contains one extensive or mass-dependent term, we can say that their product is extensive.

• In a closed path, an ideal gas’s state can change. 1→2→3→4→1. Which of the following statements regarding gas work is accurate?

Work 1→2 Work 2→3 Work 3→4 Work 4→1

(a) W > 0; W = 0; W < 0; W = 0
(b) W < 0; W = 0; W > 0; W = 0
(c) W = 0; W > 0; W = 0; W < 0

(d) W = 0; W < 0; W = 0; W > 0

• Which statement is accurate?

(a) Q for reversible < Q for irreversible and work for reversible < work for irreversible

(b) Q for reversible > Q for irreversible and work for reversible < work for irreversible

(c) Q for reversible < Q for irreversible and work for reversible > work for irreversible
(d) Q for reversible > Q for irreversible and work for reversible > work for irreversible

The reason for this is that Q for reversible is equal to (To) * (S2-S1) and Q for irreversible is equal to (To) * (S1-S2).

• The efficiency of all reversible heat engines operating between the same heat reservoirs is…….

(a) Same
(b) independent of the nature of the working substance
(c) independent of the amount of working substance
(d) all of this

• The following variables represent the state of a thermodynamic system:

(a) pressure, volume, and temperature

(b) volume only

(c) pressure only

(d) number of moles

Giving values to a large enough number of variables allows one to determine the state of a system. In mechanics, the position of the center of mass, the speed and acceleration of the body, among other measurable quantities, are used to describe the state of the body. The state of a system can be represented by specifying its pressure p, volume V, and temperature T provided the system is in equilibrium.

In thermodynamics, however, we disregard these mechanical coordinates and instead consider the interior of the system, find out directly or indirectly by experiments same measurable quantities upon which the internal state of the system for all thermodynamic purposes.

• The ideal gas model is the foundation of kinetic theory. The ideal gas is true according to the following statements, but not:

(a) The average molecular kinetic energy is directly proportional to the absolute temperature

(b) All molecules move at the same speed

(c) All molecules collide with the container’s walls in elastic collisions

(d) It is possible to ignore the attractive force between molecules

• The enthalpy of a substance is defined as

(a) H = U – PV
(b) H = U + PV
(c) H = -U + PV
(d) H = -U – PV

• Systems Y and Z are not in thermal equilibrium with system X. It’s possible that the systems Y and Z

(a) may be in thermal equilibrium

(b) None of these

(c) can be in thermal equilibrium

(d) must be in thermal equilibrium

The system consists of three parts, according to the zeroth law of thermodynamics. Say x,y, and z. A system Y is not in thermal equilibrium with either Y or Z, which is a given in the question. However, Y and Z might be in thermal equilibrium according to the Zeroth Law of Thermodynamics.

• In an isothermal process, a gas’s specific heat is

(a) infinite

(b) zero

(c) negative

(d) constant

In isothermal process temperature remains constant.

i.e. ΔT=0. Hence according to C = Q /mΔT; C=Q/mΔT ⇒ Ciso = ∞

• Work done in a quasi-static process

(a) depends on the path followed
(b) independent of the path followed
(c) depends only on the initial and final states
(d) none of the mentioned