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NEET Sample Paper NEET Sample Test Paper-86

  • question_answer
    A molecule M associates in a given solvent according to the equation\[M{{(M)}_{n}}.\] 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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