Helium gas at 102.0 kPa and 437.0 K is located within a cylinder with a piston.
ID: 1331997 • Letter: H
Question
Helium gas at 102.0 kPa and 437.0 K is located within a cylinder with a piston. Initially the gas occupies 0.4800 m3. While a constant force, F, is applied to the end of the piston so that the pressure inside the cylinder is held constant at 102.0 kPa, 6320.0 J of heat is transferred to the helium gas. The specific enthalpy of helium gas is given by the approximate relation:
H (KJ/mole) = .0208T(Kelvin)
What is the final temperature of the helium gas?
What is the final volume of the helium gas?
What is the work done by the gas?
What is the change of internal energy of the system?
Explanation / Answer
Initially using PV = nRT
102 x 10^3 x 0.48 = n x 8.314 x 437
n = 13.48 mol
Q = nCp deltaT for Isobaric process
6320 = 13.48 * (5R/2) * ( T - 437)
T - 437 = 22.56
T =459.60 K
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using PV = nRT
102 x 10^3 x V = 13.48 x 8.314 x 459.60
V = 0.505 m^3
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Work done= p * deltaV
= 102 x 10^3 x ( 0.505 - 0.480) =2548.62 J
------------------------------------
deltaU = Q- W = 6320 - 2548.62 = 3771.38 J
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