Which of the following has zero dipole moment ?

Options

A. `CO_(2)`
B. `NH_(3)`
C. `NF_(3)`
D. `H_(2)O`

Answer

To determine which of the given molecules has a zero dipole moment, we need to analyze the molecular geometry and the electronegativity of the atoms involved in each molecule. The options provided are CO2, NH3, NF3, and H2O. Let's evaluate each one step by step.

### Step 1: Analyze CO2 (Carbon Dioxide)
- **Structure**: CO2 is a linear molecule with the structure O=C=O.
- **Electronegativity**: Oxygen is more electronegative than carbon, leading to a partial negative charge on the oxygen atoms and a partial positive charge on the carbon atom.
- **Dipole Moment**: The dipole moments from each oxygen to carbon are equal in magnitude but opposite in direction. Therefore, they cancel each other out.
- **Conclusion**: The dipole moment of CO2 is zero.

### Step 2: Analyze NH3 (Ammonia)
- **Structure**: NH3 has a trigonal pyramidal shape due to the presence of a lone pair on nitrogen.
- **Electronegativity**: Nitrogen is more electronegative than hydrogen, resulting in a partial negative charge on nitrogen and partial positive charges on the hydrogen atoms.
- **Dipole Moment**: The dipole moments do not cancel out because they are directed towards the nitrogen atom.
- **Conclusion**: The dipole moment of NH3 is not zero.

### Step 3: Analyze NF3 (Nitrogen Trifluoride)
- **Structure**: NF3 also has a trigonal pyramidal shape similar to NH3.
- **Electronegativity**: Fluorine is more electronegative than nitrogen, giving fluorine a partial negative charge and nitrogen a partial positive charge.
- **Dipole Moment**: The dipole moments from the nitrogen to each fluorine do not cancel out due to their arrangement.
- **Conclusion**: The dipole moment of NF3 is not zero.

### Step 4: Analyze H2O (Water)
- **Structure**: H2O has a bent shape due to the two lone pairs on oxygen.
- **Electronegativity**: Oxygen is more electronegative than hydrogen, resulting in a partial negative charge on oxygen and partial positive charges on the hydrogen atoms.
- **Dipole Moment**: The dipole moments do not cancel out because they are directed towards the oxygen atom.
- **Conclusion**: The dipole moment of H2O is not zero.

### Final Conclusion
After analyzing all the options, we can conclude that the molecule with a zero dipole moment is **CO2** (option 1).

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