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A room contains 35 kg of dry air and 0.5 kg of water vapor. The total pressure and temperature of air in the room are 100 kPa and 25°C respectively. Given that the saturation pressure for water at 25°C, is 3.17 kPa, the relative humidity of the air in the room is
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- 67%
- 55%
- 83%
- 71%
Correct Option: D
ma = 35 kg, mv = 0.5 kg
| w = | = | = 0.01428 | ||
| mv | 35 |
| also w = 0.622 | ||
| Pa |
Pt = 100 kPa
| ∴ w = 0.622 × | ||
| Pt - Pv |
| Now, 0.01428 = 0.622 × |  | Pv |  | |||
| Pt - Pv |
Pv = 2.238 kPa
Relative humidity
| φ = | = | × 100 | ||
| Ps | 3.17 |
φ = 70.6% = 71%
