What role does the molecular interaction play in a solution of alcohol and water?
Between the molecules of alcohol as well as water, hydrogen bonding is one of the interactive forces between the molecules. When alcohol and water are mixed together, new H-bonds also develop between alcohol and water molecules but these are weaker than the previous ones. So, the magnitude of attractive forces tends to decrease and the solution shows positive deviation from Raoult's law. This will lead to increase in vapour pressure of the solution and also decrease in its boiling point.