Question

In which of the following options, the molecules are correctly arranged in the increasing order of their bond angles?

• A. \( \text{NH}_3<\text{O}_3<\text{H}_2\text{O}<\text{SO}_2 \)
• B. \( \text{H}_2\text{O}<\text{O}_3<\text{NH}_3<\text{SO}_2 \)
• C. \( \text{H}_2\text{O}<\text{NH}_3<\text{SO}_2<\text{O}_3 \)
• D. \( \text{H}_2\text{O}<\text{NH}_3<\text{O}_3<\text{SO}_2 \)

Hint:

VSEPR Theory General Rules for Bond Angles: 1. Start with the ideal angle based on the number of electron domains (Linear: 180°, Trigonal Planar: 120°, Tetrahedral: 109.5°). 2. Lone pair - lone pair repulsion>lone pair - bonding pair repulsion>bonding pair - bonding pair repulsion. 3. Lone pairs and multiple bonds occupy more space than single bonds and thus compress the angles between other bonds.

Answer 1

The Correct Option is D

To determine the correct order of molecules based on their bond angles, we need to consider the molecular geometry and the presence of lone pairs affecting these bond angles. Let's analyze each molecule:

1. \(\text{H}_2\text{O}\): The water molecule has a bent shape with two lone pairs on the oxygen. These lone pairs repel the hydrogen atoms, resulting in a bond angle of approximately 104.5°.
2. \(\text{NH}_3\): Ammonia is a trigonal pyramidal molecule with one lone pair on the nitrogen. The lone pair causes the bond angle to reduce from the ideal tetrahedral angle (109.5°) to about 107°. 
3. \(\text{O}_3\) (Ozone): Ozone has a bent shape similar to water, but with only one lone pair on the central oxygen atom. Its bond angle is slightly larger than that of water, approximately 116.8°.
4. \(\text{SO}_2\): Sulfur dioxide has a bent shape with one lone pair on the sulfur atom. Its bond angle is around 119.5°, which is larger than that of the other molecules due to the repulsion between the lone pair and bond pairs being less than in water and ozone.

Now, let's arrange these molecules in increasing order of their bond angles:

1. \(\text{H}_2\text{O}\) (104.5°)
2. \(\text{NH}_3\) (107°)
3. \(\text{O}_3\) (116.8°)
4. \(\text{SO}_2\) (119.5°)

The correct order is: \(\text{H}_2\text{O} < \text{NH}_3 < \text{O}_3 < \text{SO}_2\).