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Q & A: nitrogen vapor presure

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Most recent answer: 03/02/2009
Q:
If a known amount of liquid nitrogen were placed in a sealed container of greater volume and having the strength to container the resulting pressure what pressure would the gas inside the container reach before the rest of the liquid stops turning to gas?
- mark (age 54)
Wray, CO. U.S.A.
A:
That's a nice question. The answer is very sensitive to the temperature of the vessel. At any given temperature, there's a specific pressure for which the rates of liquid turning to vapor and vice versa just match each other, so that the net amount of liquid won't change. At the nominal boiling point of liquid nitrogen, about 77K, that pressure is exactly equal to one atmosphere, by definition. If you had higher pressure in the container, the boiling point would be at a little higher temperature. The relation between the vapor pressure and the boiling point is given by the Clausius-Clapeyron equation, which you can look up if you want to go further in this.

Mike W.

(published on 03/02/2009)

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