BCECE Medical BCECE Medical Solved Papers-2014

  • question_answer
    Which one of the following conversions involve change in both hybridisation and shape?

    A)  \[C{{H}_{4}}\xrightarrow{{}}{{C}_{2}}{{H}_{6}}\]   

    B)  \[N{{H}_{3}}\xrightarrow{{}}NH_{4}^{+}\]

    C)  \[B{{F}_{3}}\xrightarrow{{}}BF_{4}^{-}\]    

    D)  \[{{H}_{2}}O\xrightarrow{{}}{{H}_{3}}{{O}^{+}}\]

    Correct Answer: C

    Solution :

    [a] \[\underset{\begin{smallmatrix}  4bp+0lp \\  Hybridisation\,\,\,s{{p}^{3}}  \\  Structure\text{ }tetrahedral \end{smallmatrix}}{\mathop{C{{H}_{4}}}}\,\xrightarrow{{}}\underset{tetrahedral}{\mathop{\underset{\begin{smallmatrix}  4\,bp \\  s{{p}^{3}} \end{smallmatrix}}{\mathop{C{{H}_{3}}}}\,-\underset{\begin{smallmatrix}  4\,bp \\  s{{p}^{3}} \end{smallmatrix}}{\mathop{C{{H}_{3}}}}\,}}\,\] [b] \[\underset{\begin{smallmatrix}  3bp+1lp \\  Hybridisation\,\,s{{p}^{3}}  \\  Structure\text{ }pyramidal \end{smallmatrix}}{\mathop{N{{H}_{3}}}}\,\xrightarrow{{}}\underset{tetrahedral}{\mathop{\underset{\begin{smallmatrix}  4\,bp \\  s{{p}^{3}} \end{smallmatrix}}{\mathop{NH_{4}^{+}}}\,}}\,\] [c] \[\underset{\begin{smallmatrix}  3bp \\  Hybridisation\,\,s{{p}^{2}}  \\  Structure\text{ }trigonal\text{ }planar \end{smallmatrix}}{\mathop{B{{F}_{3}}}}\,\xrightarrow{{}}\underset{tetrahedral}{\mathop{\underset{\begin{smallmatrix}  4\,bp \\  s{{p}^{3}} \end{smallmatrix}}{\mathop{BF_{4}^{-}}}\,}}\,\] [d] \[\underset{\begin{smallmatrix}  2bp+2lp \\  Hybridisation\,\,s{{p}^{3}}  \\  Structure\text{ }angular \end{smallmatrix}}{\mathop{{{H}_{2}}O}}\,\xrightarrow{{}}\underset{pyramidal}{\mathop{\underset{\begin{smallmatrix}  3\,bp1lp \\  s{{p}^{3}} \end{smallmatrix}}{\mathop{{{H}_{3}}{{O}^{+}}}}\,}}\,\] Thus, conversation of \[B{{F}_{3}}\] into \[BF_{4}^{-}\] involves change in both hybridisation and shape.


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