Thermodynamics Quiz – Insight into Chemical Engineering

TD Quiz – 1

Q 1: Which of the following is not the heat engine cycle

A) refrigerator

B) steam power plant

C) mass of gas confined in a cylinder and piston machine

D) none of the above

Answer is A)

Explanation: The heat engine cycle converts heat into mechanical work by taking heat from the hot reservoir to carry out some work. In the refrigerator, work is done on the system to remove heat.

Q 2: Intensive property of a system is one whose value

A) depends on the mass of the system, like volume

B) does not depend on the mass of the system, like temperature, pressure, etc.

C) is not dependent on the path followed but on the state

D) is dependent on the path followed and not on the state

Answer is B)

Explanation: An intensive property is a physical property of a system that is independent of system size or material content.

Q 3: The temperature of an ideal gas increases from $20\;^\circ C$ to $40\;^\circ C$ while the pressure stays the same. What happens to the volume of the gas?

A) it doubles

B) it quadruples

C) it is cut to one-fourth

D) it slightly increases

Answer is D)

Explanation: At the initial state,

$P_1V_1=nRT_1\;\Rightarrow\;P_1V_1=nR(273+20)$

At the final state,

$P_2V_2=nRT_2\;\Rightarrow\;P_2V_2=nR(273+40)$

Divide both equations,

$\frac{P_2V_2}{P_1V_1}=\frac{nR\times313}{nR\times293}=\frac{313}{293}=1.1$

Given, pressure is constant

$\frac{V_2}{V_1}=1.1\;\Rightarrow\;V_2=1.1V_1$

So, the answer is D.

Q 4: Work done in a free expansion process is

A) + ve

B) -ve

C) zero

D) minimum

E) maximum

Answer is C)

Explanation: During free expansion, there is no resisting force.
Work done = Resisting force $\times$ Displacement.

Q 5: Which of the following is not correct?

A) ∆G is zero for a reversible reaction

B) ∆G is positive for a spontaneous reaction

C) ∆G is negative for a spontaneous reaction

D) ∆G is positive for a non-spontaneous reaction

Answer is B)

Explanation: The sign on ∆G must be negative for a spontaneous reaction.

Q 6: If a gas is heated against a pressure, keeping the volume constant, then the work done will be equal to

A) + ve

B) – ve

C) zero

D) anywhere between zero and infinity.

Answer is C)

Explanation: Work done = P∆V ; For constant volume, ∆V=0

Q 7: What is the cyclic integral of dQ/T for the reversible process?

A) less than zero

B) zero

C) more than zero

D) none of the above

Answer is B)

Explanation: According to Clausius’ theorem, the cyclic integral of dQ/T for a reversible cycle is zero.

Q 8: A sample of an ideal gas has an internal energy U and is then compressed to one-half of its original volume while the temperature stays the same. What is the new internal energy of the ideal gas in terms of U?

A) U

B) 1/2U

C) 1/4U

D) 2U

Answer is A)

Explanation: For an ideal gas,

$U=f\left(T\right)\Rightarrow\triangle U=mc_vdT$

Given, that the temperature is constant

$\triangle U=0\Rightarrow U_1=U_2$

Q 9: Two containers filled with 1 kg of each: water and ice at the same temperature $T = 0\;^\circ C$ Which of the following is true about the internal energy of the substances?

A) U water > U ice

B) U water < U ice

C) U water = U ice

D) U water < U ice

D) U ice < U water

Answer is D)

Explanation: Assume ice is available at $0\;^\circ C$ . To change the state of ice at the same temperature, we must supply the latent heat of fusion. As a result, liquid water at $0\;^\circ C$ has more internal energy.

Q 10: An ideal heat engine operates between two temperatures 600 K and 900 K. What is the efficiency of the engine?

A) 50 %

B) 80 %

C) 100 %

D) 33 %

Answer is D)

Explanation: Carnot efficiency is given as

$\eta=1-\frac{T_{low}}{T_{high}}$

$\eta=1-\frac{600}{900}=0.33$

Q 11: Which of the following is not the intensive property

A) pressure

B) temperature

C) density

D) heat

Answer is D)

Explanation: Work and heat are not thermodynamic properties, but rather process quantities. So, heat is neither intensive nor extensive because the concept of intensive and extensive properties only applies to physical properties that are a function of the state.

Q 12: Heat and work are

A) point functions

B) path functions

C) intensive properties

D) extensive properties.

Answer is B)

Explanation: Heat and work, both are path functions. They are path-dependent. Their magnitude depends on the path followed during a process.

Q 13: A perfect gas at 27°C is heated at constant pressure till its volume is double. The final temperature is

A) 54°C

B) 327°C

C) 108°C

D) 600°C

Answer is B)

Explanation: At the initial state,

$P_1V_1=nRT_1\Rightarrow P_1V_1=nR(273+27)$

At the final state,

$P_2V_2=nRT_2$

Divide both equations,

$\frac{P_2V_2}{P_1V_1}=\frac{nRT_2\;}{nR\times300}=\frac{T_2\;}{300}$

Given, $P_1=P_2\;\&\;V_2=2\;V_1$

$\frac{2V_1}{V_1}=\frac{T_2\;}{300}\Rightarrow T_2=600\;K$

$T(^\circ C)=T(K)-273=600-273=327\;^\circ C$

Q 14: Which of the following processes is the irreversible process

A) isothermal

B) adiabatic

C) throttling

D) none of the above

Answer is C)

Explanation: Fluid is allowed to pass through a restricted passage during the throttling process. This is accomplished by using a partially open valve or a porous plug.

The pressure drops dramatically during throttling. During the throttling process, no work is done (dW = 0), and no heat transfer (dQ = 0). It is a completely irreversible process.

Q 15: The basis for measuring the thermodynamic property of temperature is given by

A) zeroth law of thermodynamics

B) first law of thermodynamics

C) second law of thermodynamics

D) third law of thermodynamics

Answer is A)

Explanation: The zeroth law of thermodynamics provides the foundation for measuring the thermodynamic property of temperature.

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TD Quiz – 1

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