The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure, is called

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

Consider the following statements: 1. There is no change in temperature when a liquid is being evaporated into vapour 2. Vapour is a mixed phase of liquid and gas in the zone between saturated liquid line and saturated vapour line 3. The saturated dry vapour curve is steeper as compared to saturated liquid curve on a T-s diagram 4. The enthalpy of vaporization decreases with increase in pressure Which of the above statements are correct?

A

1, 2 and 3 only

B

3 and 4 only

C

1, 2 and 4 only

D

1, 2, 3 and 4

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

What is the ratio of actual mass of water vapor in a unit mass of dry air to the mass of water vapor in the same mass of dry air when it is saturated at the same temperature?

A

Moist air

B

Dry air

C

Degree of saturation

D

Saturated air

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

Consider the following statements: 1. The relative humidity of air does not change with temperature as long as specific humidity remains constant. 2. Dew-point temperature is the temperature at which condensation begins when air is cooled at constant volume. 3. Saturated air passing over a water surface does not cause change of air temperature. 4. For saturated air, dry-bulb, wet-bulb and dew-point temperatures are identical. Which of the above statements are correct?

A

1 and 2

B

2 and 3

C

1 and 4

D

3 and 4

Relative humidity is given by (where pv = Partial pressure of water vapour, pb = Barometric pressure, ps = Pressure of saturated air, pd = Pressure at dry bulb temperature, pw = Saturation pressure corresponding to wet bulb temperature, and μ = Degree of saturation)

A

0.622 Pv / (Pb - Pv)

B

μ/[1 - (1 - μ) (Ps/Pb)]

C

[Pv (Pb - Pd)]/ [Pd (Pb - Pv)]

D

None of these

Relative humidity is given by (where p_v = Partial pressure of water vapour, p_b = Barometric pressure, p_s = Pressure of saturated air, p_d = Pressure at dry bulb temperature, p_w = Saturation pressure corresponding to wet bulb temperature and $$\mu $$ = Degree of saturation)

A

$$\frac{{0.622{{\text{p}}_{\text{v}}}}}{{{{\text{p}}_{\text{b}}} - {{\text{p}}_{\text{V}}}}}$$

B

$$\frac{\mu }{{1 - \left( {1 - \mu } \right)\frac{{{{\text{p}}_{\text{s}}}}}{{{{\text{p}}_{\text{b}}}}}}}$$

C

$$\frac{{{{\text{p}}_{\text{v}}}\left( {{{\text{p}}_{\text{b}}} - {{\text{p}}_{\text{d}}}} \right)}}{{{{\text{p}}_{\text{d}}}\left( {{{\text{p}}_{\text{b}}} - {{\text{p}}_{\text{v}}}} \right)}}$$

D

None of these

At equilibrium the concentration of water in vapour phase (C^*) in kg/m³ of air space and the amount of water (m) adsorbed per kg of dry silica gel are related by, C^* = 0.0667 m. To maintain dry conditions in a room of air space 100 m³ containing 2.2 kg of water vapour initially, 10 kg of dry silica gel is kept in the room. The fraction of initial water remaining in the air space after a long time (during which the temperature is maintained constant) is

A

0.0

B

0.2

C

0.4

D

1.0

A vessel of volume 1000 m³ 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

The ratio of the actual mass of water vapour in a unit mass of dry air to the mass of water vapour in the same mass of dry air when it is saturated at the same temperature and pressure, is called

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