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Question
Assertion: When NaCl is added to water a depression in freezing point is observed.
Reason: The lowering of vapour pressure of a solution causes depression in the freezing point.
Options
Assertion and reason both are correct statements and reason is correct explanation for assertion.
Assertion and reason both are correct statements but reason is not correct explanation for assertion.
Assertion is correct statement but reason is wrong statement.
Assertion and reason both are incorrect statements.
Assertion is wrong statement but reason is correct statement.
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Solution
Assertion and reason both are correct statements and reason is correct explanation for assertion.
Explanation:
On addition of non-volatile solute (viz, NaCl) to water: NaCl solution is formed. Due to relatively lesser number of water molecules at the surface of liquid, the solution exerts a lower vapour pressure as compared to that of pure water. It is because of this lowering of vapour pressure that a depression in freezing point of water is observed.
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