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Moist air is treated as an ideal gas mixture of water vapor and dry air (molecular weight of air = 28.84 and molecular weight of water = 18). At a location, the total pressure is 100 kPa, the temperature is 30°C and the relative humidity is 55%. Given that the saturation pressure of water at 30°C is 4246 Pa, the mass of water vapor per kg of dry air is ______ grams.
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- 14.2 gm/kg of dry air
- 15.2 gm/kg of dry air
- 13.2 gm/kg of dry air
- 12.2 gm/kg of dry air
Correct Option: A
| w = 0.622 | P - Pv |
| φ = | Ps |
| ⇒ 0.55 = | Ps |
⇒ Pv = 2235.3
| w = 0.622 × | - 2235.3 | (100 × 103) |
w = 0.0142 kg/kg of dry air
w = 14.2 gm/kg of dry air
