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NEET Chemistry Solutions / विलयन Question Bank Self Evaluation Test - Solutions

  • question_answer
    A molecule M associates in a given solvent according to the equation \[M\rightleftharpoons {{(M)}_{n}}\]. For a certain concentration of M, the van't Hoff factor was found to be 0.9 and the fraction of associated molecules was 0.2. The value of n is:

    A) 3                     

    B) 5     

    C) 2                                 

    D) 4

    Correct Answer: C

    Solution :

    [c] van 't Hoff factor (i) and the degree of association are related as below: \[i=1-\alpha \left( 1-\frac{1}{n} \right)\] \[0.9=1-0.2\left( 1-\frac{1}{n} \right)\] On solving, \[\left( 1-\frac{1}{n} \right)=\frac{1}{2}\] \[\frac{1}{n}=1-\frac{1}{2}=\frac{1}{2}\] \[\therefore n=2\]


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