250+ TOP MCQs on Saturation and Answers

Basic Chemical Engineering Multiple Choice Questions on “Saturation”.

1. A vessel contains air and vapor H₂O, if the partial pressure of vapor H₂O is 4 atm and pressure of air is 1 atm, what is the fraction of vapor H₂O in vessel?
a) 0.25
b) 0.5
c) 0.75
d) 0.8

Answer: c
Clarification: yH₂O = 15/(15 + 5) = 0.75.

2. A container has vapor H₂O with partial pressure 9 atm, what is fraction of air in the vessel?
a) 0.1
b) 0.4
c) 0.7
d) 0.9

Answer: a
Clarification: Pressure of air = 1 atm, => fraction of air = 1/(1 + 9) = 0.1.

3. A system has partial pressure 500 mm Hg and the saturated water vapor has partial pressure 25 mm Hg, what is the fraction of water vapor in the system?
a) 0.01
b) 0.05
c) 0.1
d) 0.5

Answer: b
Clarification: Fraction of water vapor = 25/500 = 0.05.

4. The partial pressure of a system at 49^oC is 125 mm Hg and saturated ammonia vapor has partial pressure 20 mm Hg at 49^oC, what is the fraction of ammonia vapor in the system?
a) 0.04
b) 0.08
c) 0.16
d) 0.24

Answer: c
Clarification: Fraction of ammonia vapor = 20/125 = 0.16.

5. What is the dew point of water at standard conditions?
a) 32^oF
b) 212^oF
c) 372^oF
d) 584^oF

Answer: b
Clarification: Dew point of water at standard conditions is 100^oC = 212^oF.

6. CH₄ is burnt with 100% excess O₂ at atmospheric pressure, if CH₄ conversion is 100%, what is the pressure at dew point?
a) 0.2 atm
b) 0.4 atm
c) 0.6 atm
d) 0.8 atm

Answer: b
Clarification: CH₄ + 2O₂ -> CO₂ + 2H₂O, Basis: 100 moles of CH₄, => moles of O₂ reacted = 200, => Product contains, moles of CO₂ = 100, moles of H₂O = 200, moles of O₂ = 200. => Fraction of H₂O = 0.4, => Pressure at due point = 1*0.4 = 0.4 atm.

7. Ethane is burnt with 20% excess O₂ at 2 atm, conversion rate of ethane is 50%, what is the pressure at due point?
a) 0.45 atm
b) 0.75 atm
c) 0.9 atm
d) 1 atm

Answer: c
Clarification: C₂H₆ + 3.5O₂ -> 2CO₂ + 3H₂O, Basis: 100 moles of ethane => moles of O₂ reacted = 175, => Product contains, moles of CO₂ = 100, moles of C₂H₆ = 50, moles of O₂ = 35, moles of H₂O = 150, => fraction of H₂O = 0.45, => Pressure at due point = 2*0.45 = 0.9 atm.

8. Ethanol is burnt with required amount of O₂ at atmospheric pressure, the conversion of ethanol is 100%, what is the pressure at due point?
a) 0.2 atm
b) 0.4 atm
c) 0.6 atm
d) 0.8 atm

Answer: c
Clarification: C₂H₅OH + 3O₂ -> 2CO₂ + 3H₂O, Basis: 100 moles of ethanol, => moles of O₂ reacted = 300, => Product contains, moles of CO₂ = 200, H₂O = 300, fraction of H₂O = 0.6, => Pressure at due point = 0.6*1 = 0.6 atm.

9. 100 KPa of water vapor at 27^oC is saturated with air in a system, what is the mole fraction of air?
a) 0.230
b) 0.306
c) 0.425
d) 0.503

Answer: d
Clarification: Fraction of air = 101.3/(100 + 101.3) = 0.503.

10. 10 KPa of water vapor at 27^oC is saturated with air in a system, what is the mole fraction of air?
a) 0.21
b) 0.46
c) 0.79
d) 0.91

Answer: d
Clarification: Fraction of air = 101.3/(10 + 101.3) = 0.91.