Question

Which is the wrong result for a calorically perfect gas?

(a) e=cvT

(b) h=cpT

(c) cp and cp are functions of T

(d) For T < 1000 K, specific heats are constant

The question was posed to me during an internship interview.

My doubt stems from A Brief Review of Thermodynamics in section Compressible Flow – Preliminary Aspects of Aerodynamics

Answer 1

Right choice is (c) cp and cp are functions of T

To explain I would say: The calorically perfect gases have constant specific heats at low temperatures (T < 1000 K). cp and cp are nothing else but specific heat constants at constant pressure and temperature respectively. Internal energy and enthalpy can be given in terms of the specific heats i.e. e=cv T and h=cpT.