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A vessel of volume 1000 m<sup>3</sup> contains air which is saturated with water vapour. The total pressure and temperature are 100 kPa and 20°C respectively. Assuming that the vapour pressure of water at 20°C is 2.34 kPa, the amount of water vapour (in kg) in the vessel is approximately
A
17
B
20
C
25
D
34
Correct Answer:
17
An air-water vapour mixture has a dry bulb temperature of 60°C and a dew point temperature of 40°C. The total pressure is 101.3 kPa and the vapour pressure of water at 40°C and 60°C are 7.30 kPa and 19.91 kPa respectively.The humidity of air sample expressed as kg of water vapour/kg of dry air is
A
0.048
B
0.079
C
0.122
D
0.152
Consider the following statements and choose the correct answer:
1. A direct proportionality exists between vapour pressure and the concentration of water vapour in the atmosphere
2. Relative humidity is an expression of the ratio of the actual vapour pressure of the atmosphere when saturated at the same temperature
3. A rise or fall in temperature with no change in vapour pressure will cause a drop or rise, respectively, in relative humidity
4. A rise or fall in vapour pressure with no change in temperature will be accompanied by a rise or fall, respectively, in relative humidity
A
1, 2, 3 and 4 are true
B
Only 3 and 4 are true
C
Only 2 and 4 are true
D
Only 1, 2 and 3 are true
For water at 300°C, it has a vapour pressure 8592.7 kPa and fugacity 6738.9 kPa Under these conditions, one mole of water in liquid phase has a volume of 25.28 cm
3
and that in vapour phase in 391.1 cm
3
. Fugacity of water (in kPa) at 9000 kPa will be
A
6738.9
B
6753.5
C
7058.3
D
9000
Suppose saturated polar air has an air temperature and dew point of -10o C, and unsaturated desert air has an air temperature of 35o C and a dew point of 10o C. The desert air contains ______ water vapour and has a ________ relative humidity than the polar air.
A
More, lower
B
More, higher
C
Less, lower
D
Less, higher
One kg of saturated steam at 100°C and 1.01325 bar is contained in a rigid walled vessel. It lias a volume of 1.673 m
3
. It cools to 98°C; the saturation pressure is 0.943 bar; one kg of water vapour under these conditions has a volume of 1.789 m
3
. The amount of water vapour condensed (in kg) is
A
0.0
B
0.065
C
0.1
D
1.0
At 60° C, vapour pressure of methanol and water are 84.562 kPa and 19.953 kPa respectively. An aqueous solution of methanol at 60° C exerts a pressure of 39.223 kPa; the liquid phase and vapour phase mole fractions of methanol are 0.1686 and 0.5714 respectively. Activity co-efficient of methanol is
A
1.572
B
1.9398
C
3.389
D
4.238
A piston-cylinder device initially contains air at 150 kPa and 27°C. At this state, the volume is 400 litre. The mass of the piston is such that a 350 kPa pressure is required to move it. The air is now heated until its volume has doubled. Determine the total heat transferred to the air.
A
747 kJ
B
757 kJ
C
767 kJ
D
777 kJ
Saturated solution of benzene in water is in equilibrium with a mixture of air and vapours of benzene and water at room temperature and pressure. Mole fraction of benzene in liquid is x
B
and the vapour pressures of benzene and water at these conditions are P
v
B
and P
v
w
respectively. The partial pressure of benzene in air-vapour mixture is
A
P<sub>v</sub><sup>B</sup>
B
X<sub>B</sub>.P<sub>v</sub><sup>B</sup>
C
(P<sub>atm</sub> - P<sub>v</sub><sup>w</sup>)x<sub>B</sub>
D
X<sub>B</sub>.P<sub>atm</sub>
The ratio of actual mass of water vapour in a given volume of moist air to the mass of water vapour in the same volume of saturated air at the same temperature and pressure, is called
A
Humidity ratio
B
Relative humidity
C
Absolute humidity
D
Degree of saturation
A piston-cylinder device initially contains air at 150 kPa and 27°C. At this state, the volume is 400 litre. The mass of the piston is such that a 350 kPa pressure is required to move it. The air is now heated until its volume has doubled. Determine work done by the air.
A
120 kJ
B
130 kJ
C
100 kJ
D
140 kJ