The percent by volume of oxygen (20.95%) is constant throughout
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Question

The percent by volume of oxygen (20.95%) is constant throughout 
the troposphere. 
(a) Express this percentage as a mole fraction.

Accepted Answer

Hi everyone for this problem, we're told exhaled air has an average oxygen composition of 16% by volume, calculate the partial pressure of the oxygen, assuming a temperature of 25 degrees Celsius and 1 80 M pressure. So our goal here is to calculate partial pressure of oxygen. So partial pressure of oxygen is going to equal our mole fraction of oxygen times our total pressure. Okay, so in the problem we're told we're at 25 degrees Celsius and 18 cm. This is ideal conditions. Under ideal conditions, the mole fraction is the same as the volume fraction. So in the problem we're told that our mole fraction Or our volume is 16%. So that means our mole fraction is going to equal 16% in decimal form. This is only under ideal conditions where the mole fraction is the same as the volume fraction. So here we are able to know what the mole fraction is and we can plug that in. So our partial pressure of oxygen is going to equal our mole fraction, which is 0.16 times our total pressure we're told is 1 80 M. So that means our partial pressure of oxygen is going to equal 0.16 a. T. M. and this is our final answer. Okay, that's the end of this problem. I hope this was helpful

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