NEET Chemistry NEET PYQ-The Solid State

  • question_answer
    Structure of a mixed oxide is cubic close packed (ccp). The cubic unit cell of mixed oxide is composed of oxide ions. One fourth of the tetrahedral voids are occupied by divalent metal A and the octahedral voids are occupied by a monovalent metal B. The formula of the oxide is                                 [AIPMT (M) 2012]

    A) \[AB{{O}_{2}}\]

    B) \[{{A}_{2}}B{{O}_{2}}\]

    C) \[{{A}_{2}}{{B}_{3}}{{O}_{4}}\]

    D) \[A{{B}_{2}}{{O}_{2}}\]

    Correct Answer: D

    Solution :

    [d] According to ccp,
    Number of \[{{\text{O}}^{\text{2-}}}\] ions = 4
    So, tetrahedral void = 8
    and    octahedral void = 4
    Since, A ions occupied \[\frac{\text{1}}{\text{4}}\text{th}\] of tetrahedral void.                                         
    \[\therefore \]Number of A ions\[=\frac{1}{4}\times 8=2\] Again, B ions occupied all octahedral void.       
    \[\therefore \]Number of B ions = 4
    A : B : 0 = 2 : 4 : 4              
    = 1 : 2 : 2               
    \[\therefore \]Structure of oxide \[=A{{B}_{2}}{{O}_{2}}\]


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