Physical Chemistry Chapter 7 The phase rule When no reaction takes place, The number of constituent= the number of component Pure water: a one-component system water Mixture of ethanol and a two-component system water: ethanol water5 The Phase Rule When no reaction takes place, The number of constituent = the number of component Pure water: a one-component system Mixture of ethanol and water: a two-component system water ethanol water Physical Chemistry Chapter 7