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KVPY Sample Paper KVPY Stream-SX Model Paper-28

  • question_answer
    The vapour pressure of water at room temperature is lowered by 5% by dissolved a solute in it. What if approximate molality of solution?

    A) 2

    B) 1   

    C) 4         

    D) None of these

    Correct Answer: D

    Solution :

    \[\frac{{{P}^{o}}-{{P}_{s}}}{{{P}_{s}}}=\frac{n}{N}=\frac{n\,\,\times \,\,M}{W}=\frac{n\,\,\times \,\,M\,\,\times \,\,1000}{W\,\,\times \,\,1000}\]
    \[=\frac{molality\times M}{1000}\]
    \[Thus=\frac{100-95}{95}=\frac{m\times 18}{1000}\]
    \[\therefore \,\,\,m=2.92\]


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