Answer to Question #291997 in Physical Chemistry for Cherry

Question

At 2.00K the vapour pressure of liquid helium is 3173 PA and the heat of vaporisation is 92.048J/mol. Calculate the Lowest temperature which can be obtained by pumping on a a Dewar flask of liquid helium with a pumping system which will achieve an ultimate steady-state pressure of 133.32 PA. You may assume that the molar volume of the liquid is negligible and the vapour behaves like an ideal gas.

b) If the heat into the Dewar is 4.184J per minute, estimate the pumping speed in m^3 per minute at 133.32 PA and 309K ( temperature of gas at the pump).

Answer 1

3173=92.048× (x-2)

3173= 92.048x-184.096

3173-184.096=92.048x

= 32.47K