Question

One mole gas is first cooled from 300 K to 150 K at constant volume and then heated from 150 K to 300 K at constant pressure. The net heat absorbed by the gas is

(a) zero

(b) 150R

(c) 300R

(d) 450R

Answer 1

Correct Answer is: (b) 150R

For the first process, at constant volume,

ΔQ1 = nCv ΔT = Cv (-150).

For the first process, at constant pressure,

ΔQ2 = nCp ΔT = Cp (150).

ΔQ1 + ΔQ2 = (Cp - Cv) 150 = 150R.