Govt. Exams
Heat (Q) and Work (W) are path functions, not state functions. Internal energy, enthalpy, and entropy are state functions.
For isothermal process: ΔS = Q/T = 5000/300 = 16.67 J/K. Change in entropy is positive as heat is absorbed.
By Dalton's law: P_N2 = x_N2 × P_total = 0.40 × 5 = 2 bar
At the triple point, solid, liquid, and vapor phases are in thermodynamic equilibrium. For water, this occurs at 273.16 K and 611.657 Pa.
The Clausius statement of second law: For isolated systems, dS_universe ≥ 0. dS = 0 for reversible, dS > 0 for irreversible processes.
Work W = ∫P dV. In isochoric process, dV = 0, therefore W = 0 regardless of pressure or temperature changes.
For any cycle: ΔU_cycle = 0. First law: Q_net = W_net confirms energy conservation. 150 = 150 ✓
Using Mayer's relation: Cp - Cv = R. Therefore, Cp = 5R/2 + R = 7R/2
Entropy is defined as dS = dQ_rev/T. Units: Joules/Kelvin = J/K. This is the fundamental SI unit for entropy.
In constant volume process: W = ∫PdV = 0. From first law: ΔU = Q - W = -300 - 0 = -300 J