Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A) : The water molecule is highly polar in nature.
Reason (R) : Water molecule has bent structure.
In light of the above statements, choose the correct answer from the options given below.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

Polarity check:
- Linear \(\text{CO}_2\): Polar bonds, but symmetrical \(\rightarrow\) Non-polar (\(\mu = 0\)).
- Bent \(\text{H}_2\text{O}\): Polar bonds, asymmetrical \(\rightarrow\) Highly polar (\(\mu = 1.85 \text{ D}\)).
This V-shape prevents dipole vectors from canceling out.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Molecular polarity depends on two factors: the presence of polar covalent bonds (due to electronegativity differences between atoms) and the overall spatial geometry of the molecule.
The dipole moment (\(\mu\)) is a vector quantity that represents the charge separation within a molecule.

Step 2: Detailed Explanation:
- Assertion (A) is correct: Water (\(\text{H}_2\text{O}\)) has an exceptionally high dipole moment (\(\mu \approx 1.85 \text{ D}\)), making it highly polar.
This is because Oxygen is highly electronegative (\(\approx 3.44\)) compared to Hydrogen (\(\approx 2.20\)), creating a strong pull of electron density toward the oxygen atom.
- Reason (R) is correct: Due to \(sp^3\) hybridization of oxygen and the presence of two lone pairs, the water molecule has a bent (or V-shaped) geometry with a bond angle of approximately \(104.5^\circ\).
This bent structure is the direct reason why the individual \(\text{O}-\text{H}\) bond dipoles do not cancel each other out.
Instead, they reinforce one another, producing a net molecular dipole vector pointing from the hydrogens toward the oxygen.
If the water molecule were linear (such as carbon dioxide, \(\text{CO}_2\)), the equal and opposite bond dipoles would cancel out, leaving the molecule non-polar.
Therefore, the bent structure is the physical explanation for the highly polar nature of water, making Reason (R) the correct explanation of Assertion (A).

Step 3: Final Answer:
Both (A) and (R) are true and (R) is the correct explanation of (A).