(30 pts) Air is placed inside a chamber that is completely sealed and thermally
ID: 105135 • Letter: #
Question
(30 pts) Air is placed inside a chamber that is completely sealed and thermally insulated. That is no mass or heat energy enters or leaves the chamber. The air contains an unknown amount of water vapor. The initial temperature and pressure inside the chamber is 25°C and 1000 hPa, respectively. The volume of the chamber is slowly increased until the air inside just reaches saturation. The pressure within the chamber at that point is 800 hPa. Assume that the process occurred adiabatically. Ignore the effects of the water vapor on the value of the specific heat capacity. That is, you can use the specific heat capacity of dry air for this problem. What was the initial relative humidity of the air? Solve this exactly. That is, be sure to consider the contributions of the water vapor to the total pressure within the chamberExplanation / Answer
As relative humidity is the ratio of actual vapour pressure to saturation vapour pressure multiplied by 100.
In our case, given actual vapour pressure = 1000 hPa
Saturation vapour pressure = 800 hPa
So Relative humidity = actual vapour pressure/ Saturation vapour pressure X 100
RH = 1000/800 X 100
RH = 125 %
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