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## QuestionChemistryClass 12

The van't Hoff factor of $$0.1\:M\:La(NO_3)_3$$ solution is found to be $$2.74,$$ the percentage dissociation of the salt is:
(A) $$\;85\%$$
(B) $$\;58\%$$
(C) $$\;65.8\%$$
(D) $$\;56.8\%$$

Formula for the relation between van't Hoff factor and percentage of dissociation is as follows.
$$van't\ Hoff's\ factor(i)=1+\dfrac { \alpha }{ 100% } (n-1)$$

$$\quad \quad \quad \quad \quad \quad \quad \quad 2.74=\ 1+\dfrac { \alpha }{ 100% } (4-1)\\ \quad \quad\quad \quad \quad \quad \quad \quad \quad \alpha =58%\\$$

So percentage of dissociation $$= 58$$%.

So the answer is option B.