Finding partial pressure with only T, V and ambient P

AI Thread Summary
To find the partial pressure of nitrogen (N2) collected over water at 40°C and atmospheric pressure of 760 torr, the vapor pressure of water at this temperature is 7.3590 kPa. The total pressure (Pt) is the sum of the partial pressures of N2 and water vapor, so Pt = P(N2) + P(H2O). Given that Pt is 101.3 kPa (converted from 760 torr), the partial pressure of N2 can be calculated as P(N2) = Pt - P(H2O). The problem emphasizes that the additional information, like the volume of gas, is not necessary for solving the partial pressure, highlighting the importance of focusing on relevant data. Understanding the equilibrium vapor pressure of water is crucial in this context.
Felchi
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Homework Statement


60 L of N2 are collected over H2O at 40oC when atmospheric pressure is 760.00 torr. What is partial pressure of N2?

Homework Equations


PV=nRT
Pt=P1+P2...

Vapor pressure of H2O at 40oC:7.3590 KPa
760 torr=101.3 kPa
40oC=313oK

The Attempt at a Solution


PV-nRT
(60)101.3=313(n)8.3145
((60)101.3)/((313)8.3145)=2.166g...That doesn't help, mass of H2O unknown.

Pt=P1+P2?

Pt=101.3kPa+PN...Pt is not given...doesn't work.

Cannot assume Pt is ambient pressure because container's height affects pressure.
 
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This has nothing to do with the ideal gas law. That's just a "red herring" that they threw into confuse you. The nitrogen has been bubbled through water, so the bubbles have come to the equilibrium vapor pressure of water at the temperature of the liquid. If the partial pressure of the water is its equilibrium vapor pressure and the total pressure is 760 mm Hg, what is the partial pressure of the nitrogen?

Chet
 
And the 60L seems also thrown into confuse you - second question with that feature in a row.
 
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Let's face it - in the real world we are distracted by so many things, it is quite a good idea to add unnecessary information to problems just to make students learn what and when to ignore ;)
 
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