Alcohol and water both have a strong tendency to form intermolecular hydrogen bonding. On mixing the two, a solution is formed as a result of the formation of H-bonds between alcohol and H2 O molecules but these interactions are weaker and less extensive than those in pure H2O. Thus they show a positive deviation from ideal behavior. As a result of this, the solution of alcohol and water will have higher vapor pressure and lower boiling point than that of water and alcohol.