JEE Main & Advanced Sample Paper JEE Main - Mock Test - 6

  • question_answer
    Which of the following liquid pairs shows a positive deviation from Raoult's law?

    A) Water - Nitric acid

    B) Benzene - Methanol

    C) Water - Hydrochloric acid

    D) Acetone - Chloroform

    Correct Answer: B

    Solution :

    Positive deviations are shown by such solutions in which solvent-solvent and solute-solute interactions are stronger than the solute-solvent interactions. In such solution, the interactions among molecule becomes weaker. Therefore their escaping tendency increases which results in the increase in their partial vapour pressures.
    In pure methahol there exists intermolecular H-bonding.
    On adding benzene, its molecules come between ethanol molecules there by breaking H-bonds which weaken intermolecular forces. This result in increase in vapour pressure.

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