Answer:
90 J
Explanation:
The first law of thermodynamics says that the sum of the heat and work that goes into a system must equal its change in internal energy. For a gas, work done is equal to -1 times the area under the curve on a P-v diagram.
Work is equal to -1 times the area under the graph. For a trapezoid:
W = -½ (V₂ − V₁) (P₁ + P₂)
Plug in values (convert L to m³ and atm to Pa).
W = -½ (4 L − 2 L) (1 m³ / 1000 L) (0.5 atm + 3.5 atm) (101,325 Pa/atm)
W = -405 J
Notice the work is negative, meaning work is going out of the system. Given that 495 J of heat are going in, the change in internal energy is:
Q + W = ΔU
495 J − 405 J = ΔU
ΔU = 90 J
