JCECE Engineering JCECE Engineering Solved Paper-2009

  • question_answer
    The formula mass of Mohr's salt is\[392\]. The iron present in it is oxidised by \[KMn{{O}_{4}}\] in acid medium. The equivalent mass of Mohr's salt is

    A) \[392\]

    B) \[31.6\]

    C)  \[278\]

    D)  \[156\]

    Correct Answer: A

    Solution :

    Mohr's salt is\[(N{{H}_{4}})S{{O}_{4}}\cdot FeS{{O}_{4}}\cdot 6{{H}_{2}}O\] The equation is: \[5F{{e}^{2+}}+MnO_{4}^{-}+8{{H}^{+}}\xrightarrow{{}}\]                                 \[5F{{e}^{3+}}+M{{n}^{2+}}+4{{H}_{2}}O\] Total change in oxidation number of iron                 \[=(+3)+(-2)\]                 \[=+1\] So, equivalent wt. of Mohr's salt                 \[=\frac{Mol.\,\,wt.\,\,Mohr's\,\,salt}{1}\]                 \[=\frac{392}{1}\]                 \[=392\]


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