1. The problem statement, all variables and given/known data There is a line in a question: "Entropy of an isolated system is always maximised at equilibrium." And it is given true. But Why? 2. Relevant equations None 3. The attempt at a solution In an isolated system heat input is equal to zero. And we know that entropy= heat input/Temperature. Therefore entropy should be zero . But here its given that it is maximum, which means it is changing throughout the reaction. But according to me it should be zero throughout. So where am I wrong?