Multiple choice

A room contains 35 kg of dry air and 0.5 kg of water vapour. The total pressure and temperature of air in the room are 100 kPa and 250C respectively. Given that the saturation pressure for water at 250C is 3.17 kPa, the relative humidity of the air in the room is

  1. 67%

  2. 55%

  3. 83%

  4. 71%
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$\text{We have} \hspace{0.2cm} m_a = 35kg, m_v = 0.5kg, p_t = 100 kPa \hspace{0.2cm} and \hspace{0.2cm} p_{vs} = 3.17 kPa. \\ \text{Specific humidity} \hspace{0.5cm} W = \frac{m_v}{m_a} = \frac{0.5}{35} = 0.01428$

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