Question

5 moles of nitogen gas at 5 atm pressure contained in a 100L cylinder absorbed 30.26kJ of heat when it expanded to 200L at 2atm.
What is the change in internal energy (?U) of the gas?

Answer 1

So for the Case - 1

PV = nRT

T = PV/nR

T = (5 × 100) / 5 × 0.0821

T = 1218 K.

Case - 2

T = PV / nR

T = ( 2 × 200) / ( 5 × 0.0821 )

T= 974.42 K.

Now change in Internal energy ,

Δu = q - Δp Δv

Δu = 30.26 - [(2- 5) (200 - 100 )] / 1000

Δu = 30.26 - [(-3 × 100)]/100

Δu = 30.26 +0.3

Δu = 30.56 KJ

Hope it Helps