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

  • question_answer
    0.5 m solution of a complex of iron and cyanide ions has the depression of f.pt. to be 3.72 K (\[{{K}_{f}}\] For water \[=1.86\text{ }Kmola{{l}^{-1}}\]). The formula of the complex is:

    A) \[{{K}_{4}}[Fe{{(CN)}_{6}}]\]             

    B) \[{{K}_{2}}[Fe{{(CN)}_{4}}]\]

    C) \[{{K}_{3}}[Fe{{(CN)}_{6}}]\]             

    D) \[Fe{{\left( CN \right)}_{4}}\]

    Correct Answer: C

    Solution :

    [c] \[\Delta {{T}_{f}}(normal)={{K}_{f}}m=1.86\times 0.5=0.93{}^\circ \]Assuming 100% ionization, i = n = No. of ions per molecule \[=\frac{Observed\,\Delta {{T}_{f}}}{Normal\,\Delta {{T}_{f}}}=\frac{3.72}{0.93}=4\] \[{{K}_{3}}[Fe{{(CN)}_{6}}]\xrightarrow{{}}3{{K}^{+}}+{{[Fe{{(CN)}_{6}}]}^{3-}}\] No. of ions = 4


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