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JEE Main & Advanced Sample Paper JEE Main Sample Paper-1

  • question_answer
    Directions: Questions No. 62 are based on the following paragraph. When ammonium vanadate is heated with oxalic add solution, a compound Z is formed. A sample of Z was titrated with\[KMn{{O}_{4}}\] solution in hot acidic solution. The resulting liquid was reduced with \[S{{O}_{2}}\], the excess \[S{{O}_{2}}\]boiled off, and the liquid again titrated with \[KMn{{O}_{4}}\]. The ratio of the volumes of \[KMn{{O}_{4}}\] used in the two titrations was 5 : 1. \[KMn{{O}_{4}}\] oxidises all oxidation state of vanadium to Vanadium (+V) and \[S{{O}_{2}}\] reduces vanadium (+V) to vanadium (+IV). Read the above experiment and answer the following questions.                                      What is the oxidation state of vanadium in the compound Z?

    A)  +2                                         

    B)  +1

    C)  0

    D)  -1

    Correct Answer: C

    Solution :

     Vanadate ion \[VO_{4}^{3-}\](O. N. = 5) is reduced to \[{{V}^{x}}\] (species Z) by \[{{C}_{2}}O_{4}^{2-}\] ion in acidic medium.\[{{V}^{x}}\]is oxidised by \[MnO_{4}^{-}\] to \[{{V}^{5+}}\] \[\therefore \] \[5{{V}^{x}}+(5-x)MnO_{4}^{-}\to (5-x)M{{n}^{2+}}+5{{V}^{5+}}\]?(i) \[S{{O}_{2}}\]reduces\[{{V}^{5+}}\]to\[{{V}^{4+}}\]which in turn isoxidised to \[{{V}^{5+}}\] by \[MnO_{4}^{-}\] \[\therefore \,\,\,5{{V}^{4+}}+MnO_{4}^{-}\to \,M{{n}^{2+}}+5{{V}^{5+}}\] Volumes of \[MnO_{4}^{-}\] used in Eqs. (i), (ii) are in the ratio, of \[(5-x):1\] \[\therefore \]                  \[\frac{5-x}{1}=\frac{5}{1}\]        (given) \[x=0\]


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