The temperature and humidity of air are 27°C and 50% on a day. Calculate the amount of vapor that should be added to 1 cubic meter of air to saturate it. The saturation vapor pressure at 27°C = 3600 Pa.

Given


Temperature =27=300K


Relative humidity=50%


Volume =1m3


saturation vapor pressure (SVP) at 27°C = 3600 Pa




Vapor pressure P=0.53600=1800Pa


Molar mass of water M=16+2=18g


Let m1 be the mass of water present in 50% humid air.


Applying ideal gas equation


PV=nRT


Where V= volume of gas


R=gas constant =8.3JK-1mol-1


T=temperature


n=number of moles of gas


P=pressure of gas.


Number of moles n=




m1=13g


Required pressure for saturation =3600Pa


Let m2 be the amount of water required for saturation.


Again, applying ideal gas equation




Total excess water vapor that must be added=m2-m1=26-13=13g.


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