Why do we change the use of the heat formula in the following problem from using Cp to then using Cv:
Problem: A gas is initially at 38 ̊C and having Cp= 0.92 KJ/kg.K and Cv=0.71KJ/kg.K is
placed within a cylinder. If 8.5 KJ of heat is added to 5 kg of the gas in a non-
work flow, constant pressure process. Determine:
(a) The final gas temperature
(b) Work done on or by the gas
We use Q = mCp (T2 - T1) to find T2 because it is a constant pressure process; but then use
Q = mCv (T2 - T1) to find work.
Shouldn't we still use
Q = mCp (T2 - T1) to find Work ?