Practice question

**Isobaric process** constant pressure, work W = P ΔV = P(V₂ - V₁) = n R ΔT, for expansion ΔV positive W positive, for compression negative, heat Q = n C_p ΔT, ΔU = n C_v ΔT. Isothermal process constant temperature ΔU=0, work W = n R T ln(V₂/V₁) = n R T ln(P₁/P₂), Q = W, heat absorbed equals work done. The Kelvin-Planck statement of the Second Law states that no process can absorb heat from a single reservoir and convert it entirely into work without rejecting some heat to a colder reservoir. This limits efficiency to less than 100%. Using first law ΔU