Practice question

**Internal energy** state function depends only on temperature for ideal gas, U = f/2 n R T, change ΔU = n C_v ΔT, first law connects heat, work, internal energy, for expansion work done by gas positive, compression work done on gas negative, heat added positive. Δ U = μ C_v Δ T . μ = 0.4 , C_v = 20.8 , Δ T = 330 - 290 = 40 . Δ U = 0.4 × 20.8 × 40 = 332.8 J ≈ 333 J . Using first law ΔU = Q - W, W = ∫ P dV, isobaric W = P ΔV, isothermal