Separation Processes Questions and Answers – Liquid Activity Coefficient Models

This set of Separation Processes Multiple Choice Questions & Answers (MCQs) focuses on “Liquid Activity Coefficient Models”.

1. Which model is used for predicting liquid-phase activity coefficients?
a) Entropy models
b) Enthalpy models
c) Gibb’s free equation model
d) Keller model
View Answer

Answer: c
Explanation: The model is based on change in Gibb’s free energy.

2. The relationship between excess molar free energy and excess molar enthalpy is:
a) GE = hE – TSE
b) GE = hE + TSE
c) GE = – TSE
d) GE = hE – T
View Answer

Answer: a
Explanation: The relationship between excess molar free energy and molar enthalpy is: GE = hE – TSE.

3. For a regular solution model what is the excess molar free enrgy dependent upon?
a) Volume occupied by molecules
b) Interaction of molecules
c) Molecular size and intermolecular forces
d) Enthalpy of formation of molecules
View Answer

Answer: c
Explanation: For a regular solution model what is the excess molar free energy dependent upon the Molecular size and intermolecular forces, the former expressed in terms of liquid molar volume and the later expressed in terms of enthalpy of vaporization.
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4. Non-ideal solution effects can be incorporated in K-value formulations by:
a) Integrating for each molecule
b) Use of excess free energy
c) Use of enthalpy of vaporization
d) Use of partial fugacity coefficient ϕi
View Answer

Answer: d
Explanation: Non-ideal solution effects can be incorporated in K-value formulations by Use of partial fugacity coefficient ϕi.

5. In Margules equation, what is the one constant form equivalent to?
a) Unsymmetrical activity coefficient curves
b) Symmetrical activity coefficient curves
c) Similar partial fugacity coefficients
d) Dissimilar partial fugacity coefficients
View Answer

Answer: b
Explanation: In Margules equation, the one constant form equivalent to Symmetrical activity coefficient curves,which is rarely observed.
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6. What is the temperature dependence of van laar constant?
a) Aij = A’ij/T
b) Aij = A’ijR/T
c) Aij = A’ij/TR
d) Aij = A’ij*RT
View Answer

Answer: c
Explanation: Aij= A’ij/TR is the value of Van Laar constant.

7. When is Wilson’s equation superior to Margules and Van laar equation?
a) Non-ideal and immiscible mixtures
b) Ideal and miscible mixtures
c) Non-ideal and miscible mixtures
d) Ideal and immiscible mixtures.
View Answer

Answer: c
Explanation: Wilson’s equation superior to Margules and Van laar equation when the mixture is Non-ideal but miscible.
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8. What is the full form of NRTL model?
a) No rational two liquid model
b) Non-random three liquid model
c) Non-random two liquid model
d) Non-Rating two liquid model
View Answer

Answer: c
Explanation: The NRTL model is non-random two liquid model.

9. How does the UNIQUAC model help?
a) It helps to place calculations of activity coefficients on practical basis
b) It helps to place calculations of activity coefficients on theoretical basis
c) It helps to place calculations of activity coefficients from graph
d) It helps to provide a easier way to place calculations
View Answer

Answer: b
Explanation: The UNIQUAC model depends on the theory to give the values of activity coefficients.
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10. What must be true for two coexisting liquid phases?
a) YiL(1)xi(1) = YiL(2)xi(2)
b) YiL(1)xi(1) = xi(2)
c) YiL(1)xi(1)= YiL(2)yi(2)
d) YiL(1)xi(1) = XiL(2)xi(2)
View Answer

Answer: a
Explanation: For a liquid-liquid equilibria, for existence of two liquid phases, YiL(1)xi(1) = YiL(2)xi(2) must hold true.

Sanfoundry Global Education & Learning Series – Separation Processes.

To practice all areas of Separation Processes, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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