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college Chemistry

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An adult takes about 15 breaths per minute, with each breath having a volume of 500mL. if the air that is inhaled is "dry", but he exhaled air is 1 atm pressure is saturated with water vapor at 37 degree C(body temp), what mass of water is lost from the body in 1hr? The vapor pressure of water at 37degree C is 47.1 mmHg.

I tried doing this with partial pressures but its not coming out right.Please Help!!

  • college Chemistry -

    The volume of air inhaled in 1 hour is
    (60 min/hr)(15 br./min) = 900 breaths
    (900 br.)(0.500L/breath) = 450 L
    To find moles of H2O, use the Ideal Gas Law:
    PV = nRT
    1 atm = 760 mm Hg
    47.1mmHg/760 mmHg/atm = 0.061974 atm
    P = 0.061974 atm for water vapor
    R = 0.08206 L.atm/K.mol
    T = 273 + 37 = 310K
    Find moles of H2O:
    n = PV / RT
    Mass of H2O in grams is:
    (moles H2O)(18.015 g/mol.H2O)

  • college Chemistry -

    but the air that came out has a pressure of 1atm. doesnt that mean it has the partial pressure of air and water in it??

  • college Chemistry -

    the question was
    ....but the exhaled air at 1atm pressure is saturated with water vapor.....

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