A LevelChemistryCIETopic Questions3. Chemical Bonding3.5 Shapes of Molecules

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First teaching 2023

First exams 2025

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Shapes of Molecules (CIE A Level Chemistry)

Topic Questions

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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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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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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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