This set of Basic Chemical Engineering Multiple Choice Questions & Answers (MCQs) focuses 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
View answer
Explanation: 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
View answer
Explanation: 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
View answer
Explanation: Fraction of water vapor = 25/500 = 0.05.
4. The partial pressure of a system at 49oC is 125 mm Hg and saturated ammonia vapor has partial pressure 20 mm Hg at 49oC, what is the fraction of ammonia vapor in the system?
a) 0.04
b) 0.08
c) 0.16
d) 0.24
View answer
Explanation: Fraction of ammonia vapor = 20/125 = 0.16.
5. What is the dew point of water at standard conditions?
a) 32oF
b) 212oF
c) 372oF
d) 584oF
View answer
Explanation: Dew point of water at standard conditions is 100oC = 212oF.
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
View answer
Explanation: 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
View answer
Explanation: 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
View answer
Explanation: 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 27oC 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
View answer
Explanation: Fraction of air = 101.3/(100 + 101.3) = 0.503.
10. 10 KPa of water vapor at 27oC 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
View answer
Explanation: Fraction of air = 101.3/(10 + 101.3) = 0.91.
Sanfoundry Global Education & Learning Series – Basic Chemical Engineering.
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