Question

In a certain gas system, the pressure remains constant at 150 kPa even though 1000 J of heat is added. The volume change is 1.8 L. How much does the internal energy in joules of the system change.

Answer 1

The heat added to the system:

dQ = dU + pdV = dU + p(V₂ – V₁)

dU – change in internal energy

p – preassure

V₁ – initial volume

V₂ – final volume

$dU = dQ - p(V_2 – V_1)$

$dU = 1000 – (150 \times 10^3 \times 1.8 \times 10^{-3}) = 1000 – 270 = 730 \;J$

Answer: 730 J