VSEPR and Comparing Bond Angles

Let's take a look at this question.

VSEPR and comparing bond angles question

We need to compare the bond angles of 4 pairs of substances and determine which pair has an increase in bond angle.

That's a total of 8 substances to figure out!

If we are not familiar with the concepts of drawing dot-and-cross diagram and Valence Shell Electron Pair Repulsion (VSEPR) Theory, this question will take us a lot of time.

Check out my previous videos on the above concepts if you are interested.

Option A: CO2 to CO32-

VSEPR and comparing bond angles option A

Shape of CO2 is linear, bond angle is 180 degree.

Shape of CO32- is trigonal planar, bond angle is 120 degree.

Bond angle decreases hence this is not the answer.

Option B: BH3 to BH4-

VSEPR and comparing bond angles option B

Shape of BH3 is trigonal planar, bond angle is 120 degree.

Shape of BH4- is tetrahedral, bond angle is 109.5 degree.

Bond angle decreases hence this is not the answer.

Option C: NH2- to NH3

VSEPR and comparing bond angles option C

Shape of NH2- is bent, bond angle is 105 degree.

Shape of NH3 is trigonal pyramidal, bond angle is 107 degree.

Bond angle increases hence this is the answer that we want.

Option D: XeF2 to XeF4

VSEPR and comparing bond angles option D

Shape of XeF2 is linear, bond angle is 180 degree.

Shape of XeF4 is square planar, bond angle is 90 degree.

Bond angle decreases hence this is not the answer.

Topic: Chemical Bonding, Physical Chemistry, A Level Chemistry, Singapore

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