Covalent structure (2) Shapes & polarity questions

Assignment: Questions on Topic 4.3: Shapes & polarity

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Note that the last two questions are for only.

1

Predict the shape and bond angles of:

i. boron trichloride, BCl3

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ii. phosphoryl chloride, POCl3

2 lines
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iii. phosphine, PH3

2 lines
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iv. hydrogen cyanide, HCN

1 line
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2

Explain why sulfur dioxide molecules, SO2, have a bent shape whereas carbon dioxide molecules, CO2, are linear

5 lines
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3

Explain why C=O bonds are polar and yet the carbon dioxide molecule is non-polar.

2 lines
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4

Explain why the H-N-H angle in ammonia is smaller than the H-N-H angle in the ammonium ion.

5 lines
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5

A simplified model of benzene, C6H6, shows the six carbon atoms in a ring with alternate single and double bonds between the carbon atoms. Each carbon atom is also bonded to one hydrogen atom.

i. Based on the model described above predict the bond angle in benzene.

2 lines
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ii. In cyclohexane, C6H12 the six carbon atoms are also in a ring but are joined to each other only by single bonds. Each carbon atom is also bonded to two hydrogen atoms. Predict the bond angle in cyclohexane.

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6

Fluorine and oxygen are very electronegative elements. Explain why hydrogen fluoride, HF, and water, H2O, are very polar molecules but tetrafluoromethane, CF4, and carbon dioxide, CO2 are non- polar.

5 lines
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7

cheeky only

Predict the shape of:

i. xenon tetrafluoride, XeF4

2 lines
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ii. the iodine tetrachloride ion, ICl4–

2 lines
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iii. chlorine trifluoride, ClF3

3 lines
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8

cheeky only

Predict all the bond angles in:

i. phosphorus pentafluoride, PF5

2 lines
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ii. the phosphorus hexafluoride ion, PF6–

2 lines
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