Question

What is the variation of cp, cv and k in case of gases when the temperature increases?

(a) cp and cv decreases with temperature, and k increases

(b) cp and cv increase with temperature, and k decreases

(c) cp and cv increase with temperature, and k increases

(d) cp and cv decreases with temperature, and k decreases

I got this question in unit test.

My doubt stems from Thermodynamic Properties & Compressibility topic in portion Properties of Fluids of Fluid Mechanics

Answer 1

The correct answer is (b) cp and cv increase with temperature, and k decreases

For explanation I would say: cp is molar heat capacity at constant pressure. As temperature is increased, enthalpy increases, heat capacity increases.

Same is for cv, cp is molar heat capacity at constant volume.

However cp-cv=R and cp/cv = R

Hence, as cp, cv increases R decreases.