Which molecules has zero dipole moment ?

Options

A. `H_(2)O`
B. `CO_(2)`
C. `HF`
D. `HBr`

Explanation

To determine which molecule has zero dipole moment, we need to analyze the molecular geometry and the electronegativity of the atoms involved in each molecule. Let's go through the options step by step.

### Step-by-Step Solution:

1. **Identify the Molecules**: The question provides three molecules to analyze:
- A) H₂O (Water)
- B) CO₂ (Carbon Dioxide)
- C) HF (Hydrogen Fluoride)

2. **Analyze H₂O (Water)**:
- **Valence Electrons**: Oxygen has 6 valence electrons, and each hydrogen has 1 valence electron.
- **Bond Pairs and Lone Pairs**: H₂O has 2 bond pairs (O-H bonds) and 2 lone pairs on oxygen.
- **Hybridization**: The steric number is 4 (2 bond pairs + 2 lone pairs), leading to sp³ hybridization and a bent molecular shape.
- **Dipole Moment**: The dipole moments of the O-H bonds do not cancel out due to the bent shape, resulting in a net dipole moment. Thus, H₂O has a dipole moment.

3. **Analyze CO₂ (Carbon Dioxide)**:
- **Valence Electrons**: Carbon has 4 valence electrons, and each oxygen has 6 valence electrons.
- **Bond Pairs and Lone Pairs**: CO₂ has 2 bond pairs (C=O double bonds) and 0 lone pairs.
- **Hybridization**: The steric number is 2, leading to sp hybridization and a linear molecular shape.
- **Dipole Moment**: The dipole moments of the two C=O bonds are equal in magnitude but opposite in direction, causing them to cancel each other out. Therefore, CO₂ has zero dipole moment.

4. **Analyze HF (Hydrogen Fluoride)**:
- **Valence Electrons**: Fluorine has 7 valence electrons, and hydrogen has 1 valence electron.
- **Bond Pairs and Lone Pairs**: HF has 1 bond pair (H-F bond) and 3 lone pairs on fluorine.
- **Hybridization**: The steric number is 4, leading to sp³ hybridization and a bent shape.
- **Dipole Moment**: The H-F bond has a dipole moment directed from hydrogen to fluorine, resulting in a net dipole moment. Thus, HF has a dipole moment.

5. **Conclusion**: Among the given molecules, only CO₂ has a zero dipole moment.

### Final Answer:
The molecule with zero dipole moment is **CO₂ (Carbon Dioxide)**.