# college chemistry!! need help now!!

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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 the exhaled air at 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.

• college chemistry!! need help now!! - ,

How many moles of water per breath?

n=PV/RT

P=vaporpressure V is volume of breath
T is temp.

Now, knowing moles per breath, convert that to one hour. Finally convert moles water to grams water.

• college chemistry!! need help now!! - ,

thanks so much!! i thought it had something to do with partial pressures.

• college chemistry!! need help now!! - ,

actually, it does. You have to use the partial pressure of water in the equation, just as I said, and as GK said.

• college chemistry!! need help now!! - ,

I am irked. GK gave you a correct answer 20 min ago, and you posted again. Besides being rude, it wastes volunteers time. Please don't do that again.

• college chemistry!! need help now!! - ,

sorry about that,i am just so busy.i am a really good student at chem,just had a really big doubt.the question was confusing and i thought mayb GK mistook it as well. but it wont happen again

• college chemistry!! need help now!! - ,

http://Jiskha.com/display.cgi?id=1224463048

The moles of a gas in a mixture, in this case water vapor,depends on the partial pressure of that gas independently of any other gases present. That comes out of Dalton's Law of Partial Pressures. I gave you a complete procedure on how to calculate the moles of H2O vapor. The moles can be easily converted to grams. Do multiple postings of the same question will not get you a more detailed answer.

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