What will happen to the boiling point of the solution on mixing phenol and aniline?
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Solution and Explanation
Boiling point is the temperature at which the vapour pressure of a liquid equals the surrounding pressure. If the vapour pressure of a solution is lower, it needs a higher temperature to boil. So vapour pressure and boiling point change in opposite directions.
Step 1:
A mixture of phenol and aniline shows negative deviation from Raoult's law because of strong hydrogen bonding between the two different molecules. This makes the vapour pressure of the solution lower than expected.
Step 2:
Since the vapour pressure is lowered, more heat is needed before the vapour pressure can reach the outside pressure.
Answer: The boiling point of the solution will increase (it becomes higher than that of the pure components), because the negative deviation lowers the vapour pressure and a lower vapour pressure means a higher boiling point.
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