VSEPR and Comparing Bond Angles

Let Chemistry Guru, Singapore's renowned JC Chemistry tuition centre, guide you through this 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 CO₃^2-

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

Shape of CO₃^2- is trigonal planar, bond angle is 120 degree.

Bond angle decreases hence this is not the answer.

Option B: BH₃ to BH₄^-

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

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

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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