Anonymous asked in Science & MathematicsPhysics · 1 decade ago

What is the relative humidity in the lungs? Express as a percentage with no units.?

Suppose that air in the human lungs has a temperature of 37 degrees C and the partial pressure of water vapor has a value of 5.5 x 10^3 Pa.

1 Answer

  • 1 decade ago
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    The relative humidity is calculated by dividing the partial pressure (5.5e3 Pa) by the saturated partial pressure of water at the same temperature.

    The reference below gives a table of the saturated vapor pressure and also a formula:

    Saturated VP = [e^(77.3450 + (0.0057)T - (7,235)/T]/T^(8.2)

    The formula gives a value of 6258 Pa at T-c = 37 (implies the absolute temperature = 310.15).

    So the relative humidity would be = 5500/6258 = 87.9%.

    Hmmph, I would have guessed that the answer should be 100%: after all, the air in your lungs is in intimate contact with the blood.

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