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ASChemistryCIEExam Questions3. Chemical Bonding3.5 Shapes of Molecules

Shapes of Molecules (CIE AS Chemistry)

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3.5 Shapes of Molecules

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3.5 Shapes of Molecules

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11 mark

Hydrazine, N2H4, is a precursor for multiple pharmaceutical compounds.

Which of the diagrams below illustrate the most likely structure and bond angle of hydrazine?

  •   1-3-e-4a

  • 1-3-e-4b

  • 1-3-e-4c

  • 1-3-e-4d

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21 mark

Two boron-containing components, boron trifluoride (BF3) and sodium borohydride (NaBH4), have different molecular shapes. 

What are the shapes around the boron atom in these molecules?

 

Boron trifluoride (BF3)

Borohydride ion (BH4−)

A

Pyramidal

Tetrahedral

B

Pyramidal

Square planar

C

Trigonal planar

Tetrahedral

D

Trigonal planar

Square planar

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    31 mark

    What is the correct bond angle in a trigonal planar molecule?

    • 107°

    • 120°

    • 180°

    • 109.5°

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    11 mark

    The following equation shows the dissociation equilibrium of PCl5.

    PCl5 (g)  →  PCl3 (g)  ＋ Cl2 (g)

    The percentage yield of PCl3 differs with temperature. 

    At 160°C PCl3 yield is 13% and at 300°C yield is 100%. 

     

    The reaction is 

    Shape of PCl3 molecule

    A

    Exothermic

    Pyramidal

    B

    Exothermic

    Trigonal planar

    C

    Endothermic

    Pyramidal

    D

    Endothermic

    Trigonal planar

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      21 mark

      Which one of these species has a bond angle of 120°?

      • H3O+  

      • TlBr32-

      • BCl3

      • NH3

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      31 mark

      Ibuprofen is an anti-inflammatory drug that is used for treating pain, fever and inflammation. The structure is shown below.q8_4-2_ib_sl_medium_mcq 

      Ibuprofen

       What are the correct bond angles for a and b?

       

      a

      b

      A

      120o

      120o

      B

      107o

      109.5o

      C

      109.5o

      120o

      D

      120o

      109.5o

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        11 mark

        A student is studying conversions of different species. The two conversions below show similarities. 

        PCl5 → PCl6−

        C2H4 → C2H6

        What similar features do these two conversions have?

        • Decrease in bond angle of the species involved

        • Disappearance of a π bond

        • Change in oxidation state of an element

        • A lone pair of electrons in the product

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        21 mark

        Boron trifluoride, BF3, reacts with Trimethylamine, (CH3)3N, to form a compound of formula (CH3)3N.BF3.

        How may this reaction be written in terms of the shapes of the reactants and products?

        • 1-3-h-6a

        • 1-3-h-6b

        • 1-3-h-6d

        • 1-3-h-6c

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        31 mark

        What is the correct shape of a ClF2- ion?

        • Linear

        • T-Shaped

        • Bent

        • Trigonal planar

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