Chemical Engineering Thermodynamics MCQ Questions & Answers

51

Free energy

A) Decreases in all spontaneous (or irreversible) processes B) Change during a spontaneous process has a negative value C) Remains unchanged in reversible processes carried at constant temperature and pressure D) All of the above

Discuss

Answer & Solution

Answer: Option D

Solution:

Since for an spontaneous process $$s > dU + PdV$$
For, constant temperature and constant pressure process the above equation can be written as
$$\eqalign{ & d\left( {TS - U} \right) > PdV \cr & \Rightarrow d\left( { - A} \right) > PdV \cr & \Rightarrow {\left( {dG} \right)_{T,P}} < 0. \cr} $$
For spontaneous process (irreversible). And $${\left( {dG} \right)_{T,P}} = 0$$ for, a reversible process.

52

Co-efficient of Performance (COP) of a refrigerator is the ratio of the

A) Work required to refrigeration obtained B) Refrigeration obtained to the work required C) Lower to higher temperature D) Higher to lower temperature

Discuss

Answer & Solution

Answer: Option B

Solution:

Coefficient of performance of a refrigerator is defined as heat taken from the cold reservoir or low temperature reservoir (refrigeration) to work input for this process to take place.

53

The value of Joule-Thomson co-efficient, in case where cooling occurs after the throttling process is

A) 0 B) ∞ C) +ve D) -ve

Discuss

Answer & Solution

Answer: Option C

Solution:

For cooling to take place by throttling the Joule-Thomson coefficient must be negative. $${\left( {\frac{{\partial T}}{{\partial P}}} \right)_H} = - VE.$$

54

Fugacity is a measure of the

A) Escaping tendencies of the same substance in different phases of a system B) Relative volatility of a mixture of two miscible liquids C) Behaviour of ideal gases D) None of these

Discuss

Answer & Solution

Answer: Option A

Solution:

Fugacity is nothing but the effective pressure or escaping tendency of a particular component in a particular phase higher its value higher is the tendency to escape to other phase hence the name.

55

Fugacity is most helpful in

A) Representing actual behaviour of real gases B) Representing actual behaviour of ideal gases C) The study of chemical equilibria involving gases at atmospheric pressure D) None of these

Discuss

Answer & Solution

Answer: Option A

Solution:

Fugacity for ideal gas is equal to its pressure but for a real gas it is not equal to pressure higher the difference higher is the non-ideality actually the fugacity coefficient acts as an measure of non-ideality.

56

As the entropy of the universe is increasing, day by day, the work producing capacity of a heat engine is

A) Not changed B) Decreasing C) Increasing D) Data sufficient, can't be predicted

Discuss

Answer & Solution

Answer: Option B

Solution:

Here if we consider the universe is consisting of heat engine and corresponding high and low temperature reservoirs and to take the heat from the heat engine an surrounding as the components in the universe, than as the process goes on the temperature of the hot reservoir decreases and at some point the temperature of the universe becomes uniform and no more conversion of heat to work takes place. So, we can say as the spontaneous process is taking place in the universe the entropy is increasing of the universe and the heat engine efficiency is decreasing as the temperature is gradually becoming uniform throughout the universe.

57

Which of the following is not an equation of state?

A) Bertholet equation B) Clausius Clayperon equation C) Beattie-Bridgeman equation D) None of these

Discuss

Answer & Solution

Answer: Option B

Solution:

An equation of state must connect the basic properties of a substance like temperature, pressure and volume of the substance (system).

58

Pick out the wrong statement.

A) Minimum number of degree of freedom of a system is zero B) Degree of freedom of a system containing a gaseous mixture of helium, carbon dioxide and hydrogen is 4 C) For a two phase system in equilibrium made up of four non-reacting chemical species, the number of degrees of freedom is 4 D) Enthalpy and internal energy change is zero during phase change processes like melting, vaporisation and sublimation

Discuss

Answer & Solution

Answer: Option D

Solution:

Since, during phase change we provide latent heat (enthalpy) for breaking the intermolecular forces obviously the enthalpy changes and also since there will be the difference in potential energy between two different phases the internal energy also changes.

59

Which of the following is Virial equation of state?

A) $$\left( {{\text{p}} + \frac{{\text{a}}}{{{{\text{V}}^2}}}} \right)\left( {{\text{V}} - {\text{b}}} \right) = {\text{nRT}}$$ B) PV = nRT C) $${\text{PV}} = {\text{A}} + \frac{{\text{B}}}{{\text{V}}} + \frac{{\text{C}}}{{{{\text{V}}^2}}} + \frac{{\text{D}}}{{{{\text{V}}^3}}} + \,...$$ D) None of the above

Discuss

Answer & Solution

Answer: Option C

Solution:

The given are Van der waals equation of state and ideal equation of state and virial equation of state.

60

Which law of the thermodynamics provids basis for measuring the thermodynamic property?

A) First law B) Zeroth law C) Third law D) Second law

Discuss

Answer & Solution

Answer: Option B

No explanation is given for this question. Let's Discuss on Board

Chemical Engineering Thermodynamics MCQ Questions & Answers | Chemical Engineering