JCECE Medical JCECE Medical Solved Paper-2015

  • question_answer 12 g of a non-volatile solute dissolved in 108 g of water produces the relative lowering of vapour pressure of 0.1. The molecular mass of the solute is

    A)  80               

    B)  60        

    C)  20                

    D)  40

    Correct Answer: C

    Solution :

     From Raoults law, relative lowering in vapour pressure \[\Delta p=\frac{{{p}^{o}}-p}{{{p}^{o}}}=\frac{n}{N}=\frac{W}{m}\times \frac{M}{W}\] Here, \[w=12g;W=108g,.m=?\] \[M=18g,\Delta p=0.1\] \[\Delta p=\frac{W}{m}\times \frac{M}{W}\] or \[0.1=\frac{12}{m}\times \frac{18}{108}\] \[m=\frac{12\times 18}{10.8}=20\]

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