Which of the following has the highest dipole moment?

Options

A. `CO_2`
B. `HI`
C. `H_2O`
D. `SO_2`

Explanation

To determine which of the given molecules has the highest dipole moment, we will analyze the molecular structures and electronegativities of the compounds mentioned.

### Step-by-Step Solution:

1. **Understanding Dipole Moment**:
- The dipole moment (μ) is a measure of the separation of positive and negative charges in a molecule. It is calculated as the product of the charge (q) and the distance (d) between the charges: μ = q × d.

2. **Analyzing CO2 (Carbon Dioxide)**:
- CO2 has a linear structure with two polar bonds (C=O).
- The electronegativity of oxygen (O) is higher than that of carbon (C), resulting in a partial negative charge (δ-) on the oxygen atoms and a partial positive charge (δ+) on the carbon atom.
- However, the dipole moments of the two C=O bonds are equal in magnitude but opposite in direction, leading to a net dipole moment of zero.

3. **Analyzing HI (Hydrogen Iodide)**:
- HI has a polar bond with hydrogen (H) being less electronegative than iodine (I).
- The electronegativity of I is 2.6 and H is 2.1, resulting in a dipole moment directed from H to I.
- While HI has a dipole moment, it is relatively small compared to other molecules due to the smaller electronegativity difference.

4. **Analyzing H2O (Water)**:
- H2O has a bent molecular shape with two O-H bonds.
- The electronegativity of oxygen is 3.5 and that of hydrogen is 2.1, leading to a significant dipole moment directed towards the oxygen atom.
- The bent shape means that the dipole moments do not cancel out, resulting in a net dipole moment.

5. **Analyzing SO2 (Sulfur Dioxide)**:
- SO2 also has a bent structure with two S=O bonds.
- The electronegativity of sulfur (S) is 2.5 and that of oxygen is 3.5, resulting in a dipole moment directed towards the oxygen atoms.
- Similar to H2O, the dipole moments do not cancel out due to the bent shape.

6. **Comparing Dipole Moments**:
- Compare the dipole moments of H2O and SO2:
- H2O has a larger electronegativity difference (3.5 - 2.1 = 1.4) compared to SO2 (3.5 - 2.5 = 1.0).
- Therefore, H2O will have a higher dipole moment than SO2.
- CO2 has a net dipole moment of zero, and HI has a smaller dipole moment than both H2O and SO2.

7. **Conclusion**:
- Among the given options, H2O has the highest dipole moment due to its bent shape and significant electronegativity difference.

### Final Answer:
The molecule with the highest dipole moment is **H2O (Water)**.