Question

The molar specific heat constant pressure of an ideal gas is 7R/2. The ratio of specific heat at constant pressure to that at constant volume is?

(a) 9/7

(b) 8/7

(c) 7/5

(d) 5/7

The question was posed to me during a job interview.

My doubt is from Specific Heat and Thermodynamics topic in portion Kinetic Theory of Gases of Engineering Physics I

Answer 1

The correct option is (c) 7/5

For explanation I would say: Cp=7R/2

CV=CP-R=7R/2-R=5R/2

r=Cp/Cv = (7R/2)/(5R/2)=7/5.