Tutorial 2.3 - Shapes of molecules

Question 1

When drawing PCl5, where should you label the 90 and 120 degree angles?

Answer 1

90 degrees - on the side where it looks like a right angle

120 degrees - between the dotted and dashed Cl’s

Question 2

When drawing CO2 where should you lable the 180 degree bond angle?

Answer 2

from one bond as a semi circle all the way over to the next bond

Question 3

Explain why CH4 molecules are tetrahedral [2]

Answer 3

• electrons repel

- shape provides minimum repulsion

Question 4

Draw an H3O+ ion in 3D. Name the shape and label the H-O-H bond angle. [3]

Answer 4

• drawn same as NH3 and with one lone pair*
• 107 degrees & pyramidal
• SHOW ARROW TO H TO REPRESENT DATIVE COVALENT BOND
• 1+ charge

Question 5

Use your answer to part i and the diagram below to suggest appropriate representative bond angles for SF4. [2]

Answer 5

The diagram looked like trigonal bypyramidal PCl5 but the Cl at 90 degrees was replaced by a lone pair. So angles likely to be 90 degrees and 120 degrees but due to the lone pair any numbers just a little less than these numbers.