A gas under constant pressure of 4.5 x 105 Pa, when subjected to 800 kJ of heat, changes the volume from 0.5 m3 tp 2.0 m3. The change in internal energy of the gas is :

6.75 x 105 J 5.25 x 105 J 3.25 x 105 J 1.25 x 105 J

1.25 x 105 J

P = 4.5 x 105 Pa; dQ = 800 kJ V1 = 0.5 m3 ; V2 = 2 m3 dW = P(V2 - V1) = 4.5 x 105 (2 x 0.5)   = 6.75 x 105 J Change in internal energy : dU = dQ - dW  dU = 800 x 103 - 6.75 x 105   = 1.25 x 105 J