ASChemistryCambridge (CIE)Exam Questions3. Chemical BondingShapes of Molecules

Shapes of Molecules (Cambridge (CIE) AS Chemistry): Exam Questions

Exam code: 9701

53 mins15 questions

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Shapes of Molecules

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1
1 mark

Which diagram shows the structure and bond angle of a molecule of hydrazine, N2H4?

  • Hydrazine structure showing planar geometry with a 120° bond angle at each nitrogen
  • Hydrazine structure showing trigonal pyramidal geometry at each nitrogen with a bond angle of 107°
  • Hydrazine structure showing a bond angle of 90° at each nitrogen
  • Hydrazine structure showing 90° bond angles at each nitrogen

Choose your answer

2
1 mark

Boron trifluoride, BF3, and the borohydride ion, BH4-, have different shapes.

Which row gives the shape around the boron atom in these species?

BF3

BH4-

A

pyramidal

tetrahedral

B

pyramidal

square planar

C

trigonal planar

tetrahedral

D

trigonal planar

square planar

    Choose your answer

    3
    1 mark

    What is the bond angle in a trigonal planar molecule?

    • 107°

    • 109.5°

    • 120°

    • 180°

    Choose your answer

    1
    1 mark

    The following equation shows the dissociation equilibrium of PCl5.

    PCl5 (g) ⇌ PCl3 (g) + Cl2 (g)

    The percentage yield of PCl3 in the equilibrium mixture varies with temperature. At 160°C the yield is 13%, and at 300°C the yield is approximately 100%.

    Which row describes the forward reaction and the shape of a PCl3 molecule?

    forward reaction

    shape of PCl3 molecule

    A

    exothermic

    pyramidal

    B

    exothermic

    trigonal planar

    C

    endothermic

    pyramidal

    D

    endothermic

    trigonal planar

      Choose your answer

      2
      1 mark

      Which species has a bond angle of 120°?

      • BCl3

      • H3O+

      • NH3

      • TlBr32-

      Choose your answer

      3
      1 mark

      The structure of ibuprofen is shown.

      Skeletal formula of ibuprofen with bond angles a and b labelled at two different carbon atoms

      Which row gives the bond angles a and b?

      a

      b

      A

      107°

      109.5°

      B

      109.5°

      120°

      C

      120°

      109.5°

      D

      120°

      120°

        Choose your answer

        4
        1 mark

        Which species has a bond angle of 104.5°?

        • CH4

        • CO2

        • NH2-

        • NH4+

        Choose your answer

        1
        1 mark

        Two reactions are shown.

        PCl5 → PCl6-

        C2H4 → C2H6

        Which change occurs in both reactions?

        • a change in the oxidation state of an element

        • a decrease in bond angle

        • the disappearance of a π bond

        • the formation of a lone pair of electrons

        Choose your answer

        2
        1 mark

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

        Which equation correctly illustrates the shapes of the molecules involved in this reaction?

        • 1-3-h-6a
        • 1-3-h-6b
        • 1-3-h-6d
        • 1-3-h-6c

        Choose your answer

        3
        1 mark

        What is the shape of a ClF2- ion?

        • bent

        • linear

        • T-shaped

        • trigonal planar

        Choose your answer