CHEF has a 5 liter hydrogen liquefaction chamber with a maxi

CHEF has a 5 liter hydrogen liquefaction chamber with a maximum pressure of 100 psig and a minimum attainable temperature of 7.8 Kelvin. Before CHEF can be used to liquefy hydrogen it is necessary to pressure test the liquefaction chamber with helium. The condenser is initially filled with helium at 14 K and 100 psig (g stands for gauge, since this is gauge pressure you need to add 14.7 psi to this to convert to absolute pressure). Helium does not liquefy until near 4 Kelvin, so Ron assumes that the ideal gas law is valid. a) Use the ideal gas law to determine the mass of helium (in kilograms) in the condenser.

Solution

Given : V = 5L =5*10^-3 m³

T=14K P=114.7psia=790828.66 Pa HELIUM GAS M=4 So, R= R/M =8.314/4 =2.0785 kJ/kg K

By ideal gas equation PV = mRT   

or m = PV/RT =(790828.66*5*10^-3 /(2.0785*1000*14)) =,0.1358 kg