Consider the following five independent processes occurring at 300 K . Process H / kJ mol ⁻¹ G / kJ mol ⁻¹ A -20 -11 B -50 -47 C 30 42 D 10 10 E -10 -1 The number of processes for which the entropy change ( S ) is strictly less than -20 J K ⁻¹ mol ⁻¹ is _____.

Step-by-step solution

The relationship between change in Gibbs free energy, enthalpy, and entropy at a constant temperature is given by: G = H - T S Rearranging for S : S = H - G T We are looking for processes where S Substituting T = 300 K and converting the condition into kJ mol ⁻¹ : H - G 300 H - G G - H > 6 kJ mol ⁻¹ Let us check this condition for each process: Process A: G - H = -11 - (-20) = 9 kJ mol ⁻¹ > 6 (Satisfies) Process B: G - H = -47 - (-50) = 3 kJ mol ⁻¹ 6 (Does not satisfy) Process C: G - H = 42 - 30 = 12 kJ mol ⁻¹ > 6