This set of Chemical Engineering Questions & Answers for entrance exams focuses on “Vaporization and Energy Balances for Open, Unsteady-State Systems”.
1. For an open unsteady state system, 5 J of heat was supplied and 10 J of work was done on the system, what is the value of a change in enthalpy?
a) 5 J
b) 10 J
c) 15 J
d) 20 J
View answer
Explanation: ∆H = 5 + 10 = 15 J.
2. For an open unsteady state system, 10 J of heat was supplied and 10 J of work was done by the system, what is the value of a change in enthalpy?
a) 0
b) 10 J
c) 20 J
d) – 20 J
View answer
Explanation: ∆H = 10 – 10 = 0.
3. For an open unsteady state system, 5 J of heat was supplied and 10 J of work was done by the system, what is the value of a change in enthalpy?
a) – 5 J
b) 5 J
c) 10 J
d) 15 J
View answer
Explanation: ∆H = 5 – 10 = – 5 J.
4. For an open unsteady state system, 15 J of heat was taken off and 10 J of work was done by the system, what is the value of a change in enthalpy?
a) – 5 J
b) 5 J
c) 25 J
d) – 25 J
View answer
Explanation: ∆H = 10 – 15 = – 5 J.
5. For an open unsteady state system, 15 J of heat was supplied and -5 J of work was done on the system, what is the value of a change in enthalpy?
a) 10 J
b) – 15 J
c) 20 J
d) – 25 J
View answer
Explanation: ∆H = 15 – 5 = 10 J.
6. Which of the following represents vaporization?
a) Change of vapor to liquid
b) Change of vapor to solid
c) Change of solid to vapor
d) Change of liquid to vapor
View answer
Explanation: Vaporization is the reverse of condensation which is a change of liquid to vapor.
7. Which of the following can definitely cause vaporization?
a) Heating a liquid
b) Heating a liquid at constant pressure
c) Cooling a liquid
d) Cooling a liquid at constant volume
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Explanation: Vaporization is caused by heating a liquid at constant pressure.
8. Vaporization starts at which point?
a) Dew point
b) Bubble point
c) Triple point
d) None of the mentioned
View answer
Explanation: Bubble point is the point at which liquid starts evaporating which is the point at which vaporization starts.
9. What is the vaporization temperature of water at standard conditions?
a) 100oF
b) 212oF
c) 345oF
d) 432oF
View answer
Explanation: Vaporization temperature of water at standard conditions is 100oC = 212oF.
10. What is the point of saturation of a condensable vapor?
a) Bubble point
b) Boiling point
c) Triple point
d) Dew point
View answer
Explanation: Condensation of gas starts at its dew point.
Sanfoundry Global Education & Learning Series – Basic Chemical Engineering.
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