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JEE Main & Advanced Chemistry Solutions / विलयन Question Bank Lowering of vapour pressure

  • question_answer
    The vapour pressure of a solvent decreased by \[10mm\] of mercury, when a non-volatile solute was added to the solvent. The mole fraction of the solute in the solution is 0.2. What should be the mole fraction of the solvent, if decrease in the vapour pressure is to be \[20\,mm\] of mercury [CBSE PMT 1998]

    A)                 0.8         

    B)             0.6

    C)                 0.4         

    D)                 0.2

    Correct Answer: B

    Solution :

             \\[{{P}^{0}}-{{P}_{s}}={{P}^{0}}\times \text{mole }\,\text{fraction}\,\text{ solute}\]                 \[10={{P}^{0}}\times 0.2\]; \[20={{P}^{0}}\times n\] Þ \[n=0.4\] \ \[N=0.6\].


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