Practice question

**Carnot engine** reversible engine operating between T_h and T_c has maximum efficiency η =1 - T_c/T_h, T in kelvin, e.g., T_h=400 K T_c=300 K η=0.25, real engines less due to irreversibilities, second law defines direction of spontaneous processes and entropy increase. Adiabatic: T₁ V₁^γ-1 = T₂ V₂^γ-1 , V₁ = (μ R T₁)/(P₁) = (0.4 × 8.3 × 340)/(7) ≈ 161.37 L , V₂ = (0.4 × 8.3 × T₂)/(1) = 3.32 T₂ . 340 × 161.37⁰.4 = T₂ × (3.32 T₂)⁰.4 . Approximate: T₂ ≈ 245 K . Using first law ΔU = Q - W, W = ∫ P dV, isobaric W =