Question

If 15 gm of air is heated from 0℃ to 5℃ at constant volume by adding 150 calorie of heat the change in internal energy of air

Answer 1

Oxygen is a diatomic gas

number of degrees of freedom = n = 5

specific heat at constant volume = Cv = �R = �R 2 2

i.e, Cv = 2.5 x 8.31 = 20.78 J mor1 K"1

Heat supplied to raise the temperature of 5 moles of oxygen from 10�C to 20�C is d

= 5 x 20.78x 10 = 1039 J

Work done =dW = Q (v Volume is constant)

From the First law of thermodynamics, change in internal energy is dU = dQ - dW

= 1039-0 = 1039 J