# Separation Processes Questions and Answers – Non-ideal Thermodynamic Property Models

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This set of Separation Processes Multiple Choice Questions & Answers (MCQs) focuses on “Non-ideal Thermodynamic Property Models”.

1. What is the p-v-T equation of state?
a) Relationship between volume and temperature
b) Relationship between pressure, molar volume and temperature
c) Relationship between pressure and temperature
d) Relationship between pressure and molar volume

Explanation: The Relationship between pressure, molar volume and temperature is the p-v-T equation of state.

2. What does the ideal gas equation neglects?
a) Temperature of molecules
b) Friction between molecules
c) Volume occupied by the molecules
d) Pressure occupied by the molecules

Explanation: The ideal gas equation neglects the volume occupied by the molecules hence it is only applicable at low pressures.

3. What is the van der waal’s equation of non-ideal gas?
a) [P + a(n/v)2](v/n –b) =RT
b) [P + a(n/v)2] =RT
c) [P + (n/v)2](v/n –b) =RT
d) [P + a(n/v)2](v/n ) =RT

Explanation: [P + a(n/v)2](v/n –b) =RT is the correct equation for real gases.

4. What is the formula for acentric factor?
a) Z = (-log(Ps/Pc)Tr=o.7) – 1000
b) z = (-log(Ps/Pc)Tr=o.7) – 1.000
c) ω = (-log(Ps/)Tr=o.7) – 1.000
d) ω = (-log(Ps/Pc)Tr=o.7) – 1.000

Explanation: ω = (-log(Ps/Pc)Tr=o.7) – 1.000 is the correct equation for determining acentric factor based on the law of corresponding states.

5. What is the value of ω for symmetric molecules?
a) 1
b) 0.264
c) 0
d) 0.490

Explanation: The value of ω is 0 for symmetric molecules.

6. How can the compressibility factor be determined form generalized equation and Redich-kwong equation?
a) Z3 – Z2 + (A-B-B2)Z – AB =0
b) Z3 – Z2 + (A-B-B2) – AB =0
c) Z3 – Z2 + (A-B-B2)Z – A =0
d) Z3 – Z2 + (A-B)Z – AB =0

Explanation: The generalized equation PV= ZRT and the redich kwong equation are combined to give Z3 – Z2 + (A-B-B2)Z – AB =0 where A and B are constants which can be determined.

7. If A =0.2724 and B= 0.05326 find the value of compressibility factor Z.
a) 0.7867
b) 0.7314
c) 0.8656
d) 10.435

Explanation: Z3 – Z2 + (A-B-B2)Z – AB =0 is the equation used. Hence by solving Z3 – Z2 + (0.2724-0.05326-0.053262)Z – 0.2724*0.05326 =0 we get Z= 0.7314.

8. What is the correct representation of Soave-Redich-Kwong equation?
a) P = [RT/v-b] – [a/v2+bv+a].
b) P = [RT/v-b] – [a/v2+bv].
c) P = [RT/v-b] – [a/v2+bv+b].
d) P = [RT/v-b] – [a/v2].

Explanation: P = [RT/v-b] – [a/v2+bv] is the Soave-Redich-Kwong equation.

9. What is the value of b if the temperature is 477.6K and the saturation pressure is 2829kPa?
a) 836.7 units
b) 2334.666 units
c) 0.0626 units
d) 0.4356 units

Explanation: b = 0.08664RT/Pc is the equation is used to determine b.
Hence b= 0.08664 *8.314*477.6/2829000= 2334.666 units

10. If the critical temperature of propane is 369.8K and temperature of mixture is 477.6K and the saturation pressure is 4250kPa , what is the value of a?
a) 234.5 units
b) 678.9 units
c) 765.6 units
d) 836.7 units 