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Question
Answer the following.
How vapour pressure lowering is related to a rise in the boiling point of solution?
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Solution
- At the boiling point of a liquid, its vapour pressure is equal to 1 atm.
- In order to reach boiling point, the solution and solvent must be heated to a temperature at which their respective vapour pressures attain 1 atm.
- At any given temperature the vapour pressure of a solution is lower than that of pure solvent. Hence, the vapour pressure of solution needs a higher temperature to reach 1 atm than that of needed for vapour pressure of solvent. Therefore, vapour pressure lowering causes a rise in the boiling point of a solution.
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