Chemical Engineering Thermodynamics MCQ Questions & Answers

61

The value of C_p & C_v respectively for monoatomic gases in Kcal/kg Mole . °K are

A) 5 & 3 B) 3.987 & 1.987 C) 1.987 & 0.66 D) 0.66 & 1.987

Discuss

Answer & Solution

Answer: Option A

Solution:

These values are experimental values. And the values are $${C_p} = 5$$ and $${C_v} = 3$$ for mono-atomic gases.

62

Gibbs-Duhem equation

A) States that n₁dμ₁ + n₂dμ₂ + .... n_jdμ_j = 0, for a system of definite composition at constant temperature and pressure B) Applies only to binary systems C) Finds no application in gas-liquid equilibria involved in distillation D) None of these

Discuss

Answer & Solution

Answer: Option A

Solution:

The Gibbs-Duhem equation states that $$\sum\nolimits_{i\, = \,1}^n {} {n_i}d{\mu _i} = 0$$
Here the addition to be done for an particular component in different phases.

63

Pick out the correct statement.

A) The available energy in an isolated system for all irreversible (real) processes decreases B) The efficiency of a Carnot engine increases, if the sink temperature is decreased C) The reversible work for compression in non-flow process under isothermal condition is the change in Helmholtz free energy D) All of the above

Discuss

Answer & Solution

Answer: Option D

Solution:

All the given statements are correct the $${\left( {dG} \right)_{T,P}} < 0.$$
For irreversible process and the efficiency is inversely proportional to sink temperature for an carnot engine and by the definition of Helmholtz energy itself the change in Helmholtz energy represents the negative of work done in an reversible isothermal process.

64

The unity of Planck's constant 'h' in the equation, E = hv is

A) J/s B) J.S C) J/kmol D) Kmol/J

Discuss

Answer & Solution

Answer: Option B

Solution:

The unit is J. Sec.

65

For the reversible exothermic reaction, N₂ + 3H₂ ⇋ 2NH₃, increase of pressure would

A) Shift the equilibrium towards right B) Give higher yield of NH₃ C) Both A and B D) Neither A nor B

Discuss

Answer & Solution

Answer: Option C

Solution:

By Le Chatelier's principle the increase in pressure shifts the equilibrium towards less number of moles side so, here the equilibrium shifts towards the right side thereby, increasing the concentration of $$N{H_3}.$$

66

If heat contents of CH₄, C₂H₄ and C₃H₈ are -17.9, 12.5 and -24.8 kcal/mole respectively, than ΔH for the reaction CH₄(g) + C₂H₄(g) ⇋ C₃H₈(g) will be __________ Kcal.

A) -19.4 B) -30.2 C) 55.2 D) -55.2

Discuss

Answer & Solution

Answer: Option A

Solution:

Since the enthalpy change $$=$$ enthalpy or heat content of the products $$–$$ enthalpy or heat content of the reactants $$= -24.8+17.9-12.5 = -19.4.$$

67

Pick out the wrong statement.

A) A refriferation cycle violates the second law of thermadynamics B) Refrigeration cycle is normally represented by a temperature vs. entropy plot C) In a refrigerator, work required decreases as the temperature of the refrigerator and the temperature at which heat is rejected increases D) One ton of refrigeration is equivalent to the rate of heat absorption equal to 3.53 kW

Discuss

Answer & Solution

Answer: Option A

Solution:

Since refrigeration cycle works by taking some help or work from the surrounding to transfer heat from low temperature reservoir to high temperature reservoir it is following the second law of thermodynamics namely Clausius statement.

68

The work done in an adiabatic change in a particular gas depends upon changes in the __________ only.

A) Temperature B) Specific heat C) Volume D) Pressure

Discuss

Answer & Solution

Answer: Option A

Solution:

Since under adiabatic process $$dU=$$ work done, and for ideal gas since change in internal energy is solely dependent on temperature it implies that the work done is only dependent on temperature. Here in the question the ideal gas should be used instead of any particular gas.

69

The expression, nC_v(T₂ - T₁), is for the __________ of an ideal gas.

A) Work done under adiabatic condition B) Co-efficient of thermal expansion C) Compressibility D) None of these

Discuss

Answer & Solution

Answer: Option A

Solution:

From the above question explanation we can write $$n{C_v}\left( {{T_2} - {T_1}} \right) = $$ work done
Since, internal energy for ideal gas $$dU = n{C_v}\left( {{T_2} - {T_1}} \right).$$

70

The chemical potential of any constituent of an ideal solution depends on the __________ of the solution.

A) Temperature B) Pressure C) Composition D) All of the above

Discuss

Answer & Solution

Answer: Option D

Solution:

The ideal solution behaves like a pure solution since pure component chemical potential depends upon temperature, pressure and composition the ideal solution chemical potential also depends on the same.

Chemical Engineering Thermodynamics MCQ Questions & Answers | Chemical Engineering