Question

The angle formed between oxygen and hydrogen in water molecule is

• A. \( 50^{\circ} \)
• B. \( 75^{\circ} \)
• C. \( 100^{\circ} \)
• D. \( 105^{\circ} \)

Hint:

Remember: \( 104.5 \) is the magic number for water.
This "Bent" shape is what makes life possible! If water were linear (\( 180^{\circ} \)), it wouldn't be polar, and it wouldn't be the "Universal Solvent."

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks for the bond angle between the two hydrogen atoms and the central oxygen atom in a molecule of water (\( H_2O \)).
Detailed Explanation:

• Molecular Geometry:
Water has a "bent" or "V-shaped" molecular geometry.
The central oxygen atom has four pairs of electrons: two bonding pairs (with Hydrogen) and two lone pairs.

• VSEPR Theory:
According to the Valence Shell Electron Pair Repulsion theory, lone pairs occupy more space than bonding pairs.
The repulsion between the two lone pairs on the oxygen atom pushes the two \( O-H \) bonds closer together.
In a perfect tetrahedron, the angle would be \( 109.5^{\circ} \). Due to the lone pair repulsion, this angle is squeezed down to approximately \( 104.5^{\circ} \).

• Polarity:
This asymmetric, bent shape is the reason why water is a polar molecule. The oxygen side has a partial negative charge, and the hydrogen side has a partial positive charge.
This polarity leads to hydrogen bonding, giving water its high boiling point and excellent solvent properties.

• Analyzing Options:
The most accurate approximation provided in the options is \( 105^{\circ} \).

Step 2: Final Answer:
The bond angle in a water molecule is approximately \( 105^{\circ} \) (specifically \( 104.5^{\circ} \)).