Question

Propane gas at 100 c is compressed isothermally from an initial pressure of 1 bar to a final pressure of 5 bar.

a. Determine the Delta H of the process

b. Determine the Delta S of the process

c. Comment on the differences between a closed and an open system undergoing this change in terms of Q,W,H and S.

Answer 1

a) Delta H = delta U +Delta (PV)

delta U = o for isothermal process, for ideal gas Delta (PV) = 0 9assuming propane as ideal gas)

Work done in isothermal process = RT ln(P1/P2) = 8.314*(273+100)*ln(1/5) = -4991.1 J/mol

Q = Delta U +W = 0 -4991.1 = -4991.1 J/mol

B) Delta S = -DeltaQ/T = 4991.1/373 = 13.38 J/mol.k

C) closed system can exchange only energy with surrounding however open syatem can change mass as well as energy with system

This is basically a closed system because Q is negative and entropy of the sytem is increasing and work is delivered by ststem to surrounding..