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January 30, 2015

January 30, 2015

Posted by **Jay** on Friday, March 2, 2007 at 10:07am.

Add the partial pressures of the air and that of the vaporized helium.

120 mL of LHe has a mass of 0.147 g/ml x 120 mL = 17.64 g. That is = 4.406 moles. From that and the volume and temperature, you can calculate the partial pressure of He, using

P = nRT/V

R = 8.205*10^-2 atm*L/mole K

P(He)= 107.7 atm

The air partial pressure is much less. It starts out at 1.0 atm at 118K and rises to 1.0 x (298/118) = 2.5 atm at the higher temperature of 298 K.

Add the two partical pressures for the total pressure.

I don't guarantee my numbers, so check them yourself. The method should work.

thanks

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