The enthalpy change ( H ) and entropy change ( S ) for five different processes are given below. Assume that H and S are independent of temperature. Process H / kJ mol ⁻¹ S / J K ⁻¹ mol ⁻¹ 1 -45 -100 2 -20 -80 3 -60 -75 4 45 100 5 -40 -80 The number of processes that are spontaneous at 300 K but become non-spontaneous at 600 K is _____.

Step-by-step solution

For a process to be spontaneous, the change in Gibbs free energy ( G ) must be negative. G = H - T S The process is spontaneous at 300 K ( G₃₀₀ 0 ). This behavior (spontaneous at low temperatures and non-spontaneous at high temperatures) occurs only when both H Let us evaluate the crossover temperature for each process (ensuring units are matched by multiplying H by 1000 ): Process 1: T_ eq = -45000 -100 = 450 K . Since 300 Process 2: T_ eq = -20000 -80 = 250 K . At 300 K , T > T_ eq , so G > 0 . It is non-spontane