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# Separation Processes MCQ’s – Non-ideal Thermodynamic Property Models

1 - Question

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

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

2 - Question

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

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

3 - Question

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

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

4 - Question

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

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Answer: d.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 - Question

What is the value of ω for symmetric molecules?

a) 1

b) 0.264

c) 0

d) 0.490

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Answer: cExplanation: The value of ω is 0 for symmetric molecules.

6 - Question

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

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Answer: a.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 - Question

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

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Answer: bExplanation: 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 - Question

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].

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

9 - Question

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

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Answer: cExplanation: 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 - Question

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

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Answer: dExplanation: a= 0.42748R2Tc2.5/PcT0.5 is the equation used to calculate a. Hence a= 0.427(8.314)2(369.8)2.5/4250000*(477.6)0.5.