Chemical Engineering

Modeling and Predicting Vapor Pressure

Question 1
Marks : +2 | -2
Pass Ratio : 100%
What is the pressure of a gas at T = 227oC, it is given that A = 5, B = 4 X 104 and C = 0 if T is in kelvin and p in mm Hg?
0.024 mm Hg
0.049 mm Hg
0.075 mm Hg
0.096 mm Hg
Explanation:
ln p* = A – B/(C + T), => ln p = 5 – 4 X 103/(273 +227) = -3, => p = 0.049 mm Hg.
Question 2
Marks : +2 | -2
Pass Ratio : 100%
Pressure of a gas at temperature T is P, What is the pressure of the gas at 2T, use B = 1?
Pe1/T
Pe1/2T
Pe1/3T
Pe1/4T
Explanation:
ln P/P2 = 1*(1/2T – 1/T), => P2 = Pe1/2T.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
What is the pressure of CO2 at 325 K, if it is given that pressure at 330 K is 6 Pa, and pressure at 320 K is 4 Pa?
4.5 Pa
5 Pa
5.5 Pa
6 Pa
Explanation:
Using linear interpolation, P325K = 4 + (325 – 320)*(6 – 4)/(330 – 320) = 4 + 5*2/10 = 5 Pa.
Question 4
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Pass Ratio : 100%
At which of the following values of pressure a solid melts first?
5 atm
720 mm Hg
500 KPa
40 Torr
Explanation:
A solid melts first at the highest pressure which is 5 atm.
Question 5
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If the pressure of a gas at 27oC is 15 mm Hg, what will be its pressure at 127oC, use B = 5 X 103, C = 0, T is in kelvin and P is in mm Hg?
579 mm Hg
775 mm Hg
961 mm Hg
999 mm Hg
Explanation:
ln P1/P2 = B (1/T2 – 1/T1), => ln 15/P2 = 5 X 103 (1/400 – 1/300), P2 = 961 mm Hg.
Question 6
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A liquid evaporates first at which of the following conditions?
High attraction forces
Low attraction forces
Low vapor pressure
High boiling point
Explanation:
A liquid evaporates first at low attraction forces.
Question 7
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Temperature of SO2 at 5 Pa is 395 K and at 10 Pa temperature is 420 K, what is the temperature at 6 Pa?
400 K
405 K
410 K
415 K
Explanation:
Using linear interpolation, T6Pa = 395 + (6 – 5)*(420 – 395)/(10 – 5) = 395 + 5 = 400 K.
Question 8
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Pass Ratio : 100%
At triple point, vapor pressure of ice is given by ln p* = 18 – 2560/T, and vapor pressure of water is given by ln p* = 28 – 5120/T, what is the temperature at triple point?
225 K
256 K
320 K
400 K
Explanation:
At triple point pressure and temperature of all the phases becomes same, => 18 – 2560/T = 28 – 5120/T, => 10 = 2560/T, => T = 256 K.
Question 9
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Pass Ratio : 100%
Pressure of a gas at 127oC is 10 mm Hg and the pressure at 527oC is 20 Pa, what is the value of B?
225.1
365.5
499.2
554.5
Explanation:
ln 10/20 = B (1/800 – 1/400), => B = 554.5.
Question 10
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Pass Ratio : 100%
A material’s mass is given by the equation, m = 32P0.02/T0.5, where T is in Kelvin, m is in Kg and P is in mm Hg, what is the mass of material at 127oC, use A = 10, B = 6 X 103 and C = 0?
1.44 Kg
1.69 Kg
1.96 Kg
2.25 Kg
Explanation:
ln p* = A – B/(C + T) = 10 – 6 X 103/(400) = -5, => p = 0.0067 mm Hg, => m = 32*(0.0067)0.02/4000.5 = 1.44 Kg.