A gas is compressed from an initial volume of 5.65 L to a final volume of 1.21 L by an external pressure of 1.00 atm. During the compression, the gas releases 128 J of heat. What is the change in internal energy of the gas? Express your answer to three significant figures.

The change in internal energy of the gas is 578 J

Explanation:

∆U = Q - W

Q = 128 J

W = P(V2 - V1)

P = 1 atm = 101325 N/m^2

V2 = 1.21 L = 1.21/1000 = 1.21×10^-3 m^3

V1 = 5.65 L = 5.65/1000 = 5.65×10^-3 m^3

W = 101325(1.21×10^-3 - 5.65×10^-3) = 101325 × -4.44×10^-3 = -449.883J

∆U = 128 - (-449.883) = 128 + 449.883 = 577.883 = 578 J (to 3 significant figures)