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KVPY Sample Paper KVPY Stream-SX Model Paper-26

  • question_answer
    Gradual addition of potassium iodide solution to \[\operatorname{Bi}{{\left( N{{O}_{3}} \right)}_{3}}\]solution initially produces a dark brown precipitate which dissolves in excess of KI to give a clear yellow solution. Identify the yellow precipitate.

    A) \[{{\operatorname{I}}_{2}}\]    

    B) \[K{{\operatorname{I}}_{3}}\]

    C) \[\operatorname{Bi}{{\left( OH \right)}_{2}}\]     

    D) \[\operatorname{Bi}\left( OH \right){{\left( N{{O}_{3}} \right)}_{2}}\]

    Correct Answer: B

    Solution :

    At first, \[Bi{{(N{{O}_{3}})}_{3}}\]undergoes hydrolysis nitric acid is formed. Which oxidises KI to iodine. The liberated iodine dissolves in KI to from yellow solutions of \[K{{I}_{3}}\].
    \[Bi{{(N{{O}_{3}})}_{3}}+{{H}_{2}}O\xrightarrow{{}}[Bi(OH){{(N{{O}_{3}})}_{2}}]+HN{{O}_{3}}\]
    \[2HN{{O}_{3}}\xrightarrow{{}}{{H}_{2}}O+2N{{O}_{2}}+O\]
    \[2KI+{{H}_{2}}O+O\xrightarrow{{}}2KOH+\underset{\operatorname{Drak}\,brown}{\mathop{{{I}_{2}}}}\,\]
    \[{{\operatorname{I}}_{2}}+KI\xrightarrow{{}}\underset{yellow\,\,solution}{\mathop{K{{I}_{3}}}}\,\]


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