# Question: an ideal gas with cp 72r and cv ...

###### Question details

An ideal gas with Cp = (7/2)R and Cv = (5/2)R undergoes the
following reversible

changes in a series of nonflow processes:

a. From an initial state of 70(°F) and 15(psia), it is compressed
adiabatically to 75(psia).

b. It is then cooled to 70(°F) at a constant pressure of
75(psia).

c. Finally, the gas is expanded isothermally to its original
state.

Calculate Q, WEC, ΔU, and ΔH for each of the three processes and
for the entire cycle. Next,

calculate Q, WEC, ΔU, and ΔH for exactly the same changes in state
that you computed above for

(a)-(c), but now assuming that each process is irreversible with an
efficiency of 75 percent

compared to reversible operation. Specifically, if the reversible
process produces 10 BTU of

work, the irreversible process should produce 0.75(10)=7.5 BTU, and
if the reversible process

requires BTU kJ of work, the irreversible process should require
10/0.75 = 13.33 BTU. Use the

exact same initial and final states you already computed (this will
require nonzero heat flow in

part (a)).