What is the % relative humidity at 25 oC and 0.01876 atm if the vapor pressure of water is 23.76 mm Hg?
Correct answer: C. 60%
- A. 40%
- B. 50%
- C. 60%
- D. 70%
Explanation
Relative humidity is the ratio of the partial pressure of water vapor present in the air to the vapor pressure of water at a particular temperature, expressed as a percentage. In this question, we are given the vapor pressure of water (23.76 mm Hg) and the temperature (25 oC). We can use the formula: Relative Humidity = (Partial Pressure of Water Vapor / Vapor Pressure of Water) x 100 We need to first convert the given pressure of 0.01876 atm to mm Hg. 1 atm = 760 mm Hg, so 0.01876 atm = 14.268 mm Hg. Then, we can substitute the values in the formula: Relative Humidity = (14.268 / 23.76) x 100 = 60% Therefore, the % relative humidity at 25 oC and 0.01876 atm is 60%.
This question appeared on the NUMS 2019 (cancelled sitting) paper, which you can sit online with every answer explained.
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About Evaporation, Boiling Point and Vapour Pressure
Evaporation is the escape of higher-energy molecules from a liquid surface, while vapour pressure is the pressure exerted by vapour in equilibrium with that liquid. The topic distinguishes evaporation from boiling and relates both to temperature, intermolecular forces, surface area, atmospheric pressure and the boiling point.
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