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Old Aug 4th 2009, 02:35 AM   #1
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Unhappy humidity questions

A volume Vi = 24.2 L of air at temperature T = 21 C is compressed at constant temperature to a volume Vf = 11.2 L. The relative humidity of the air before compression is R = 56.7 %. Saturated water vapour in air at this temperature has a vapour pressure vp = 2.5 kPa and a density of ρ = 18.4 g.m−3.

(a) What is the partial pressure of the water vapour in the air before compression?
(b) What is the factor by which each non-condensing component of air (e.g. oxygen , nitrogen, etc) has its partial pressure increased in the compression?
(c) What is the density the water vapour would have had following compression if it behaved like an ideal gas instead of experiencing partial condensation?
(d) What is the density of water vapour in the air following compression?
(e) What mass of water condenses out because of the compression?

could someone please help, i can't seem to find a question like this in any of the books, so need help with solving them.
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Old Aug 4th 2009, 03:11 PM   #2
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For (a) you should try using the formula
Relative Humidity = Partial Pressure / Vp X 100
And rearrange for Partial Pressure
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