AFMC AFMC Solved Paper-2007

  • question_answer
    A brown ring appears in the test for

    A) nitrate                                 

    B) nitrite

    C) bromide                              

    D) iron

    Correct Answer: A

    Solution :

    At the junction of salt formation and \[\text{FeS}{{\text{O}}_{\text{4}}}\]solution with cone. \[{{\text{H}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}\]a brown ring is obtained \[\text{(FeS}{{\text{O}}_{4}}\text{.NO)}\text{.}\] \[\underset{\begin{smallmatrix}  \text{nitrate}\,\text{salt} \\  \text{soluble}\,\text{in}\,\text{water} \end{smallmatrix}}{\mathop{NO_{3}^{-}+}}\,6FeS{{O}_{4}}+3{{H}_{2}}S{{O}_{4}}\to 3F{{e}_{2}}{{(S{{O}_{4}})}_{3}}\] \[+2NO+3{{H}_{2}}O\] \[FeS{{O}_{4}}+NO\to \underset{brown\,ring}{\mathop{FeS{{O}_{4}}.NO}}\,\]


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