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Question
What role does the molecular interaction play in a solution of alcohol and water?
Solution 1
In pure alcohol and water, the molecules are held tightly by a strong hydrogen bond. The interaction between the molecules of alcohol and water is weaker than the alcohol-alcohol and water-water interactions. As a result, when alcohol and water are mixed, the intermolecular interactions become weaker and the molecules can easily escape. This increases the vapour pressure of the solution, which in turn lowers the boiling point of the resulting solution.
Solution 2
Alcohol and water both have a strong tendency to form intermolecular hydrogen bonds. On mixing the two, a solution is formed as a result of the formation of H-bonds between alcohol and H2O molecules, but these interactions are weaker and less extensive than those in pure H2O. Thus, they show a positive deviation from ideal behaviour. As a result of this, the solution of alcohol and water will have a higher vapour pressure and a lower boiling point than that of water and alcohol.
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