The correct order of dipole moments of `HF, H_(2)S and H_(2)O` is :

Options

A. `HF lt H_(2)S lt H_(2)O`
B. `HF lt H_(2)S gt H_(2)O`
C. `HF gt H_(2)S gt H_(2)O`
D. `HF gt H_(2)O gt H_(2)S`

Explanation

To determine the correct order of dipole moments for the molecules HF, H₂S, and H₂O, we will analyze the factors that contribute to dipole moments, including electronegativity differences and molecular geometry.

### 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 (R) between the centers of positive and negative charges:
\[ \mu = Q \times R \]
- A higher dipole moment indicates a more polar bond.

2. **Electronegativity Values**:
- Electronegativity is the tendency of an atom to attract electrons in a bond. The electronegativity values for the relevant atoms are:
- Fluorine (F): 4.0
- Oxygen (O): 3.5
- Sulfur (S): 2.5
- From these values, we can see that F > O > S.

3. **Analyzing Each Molecule**:
- **HF (Hydrogen Fluoride)**:
- The bond between H and F is highly polar due to the large electronegativity difference (4.0 - 2.1 = 1.9).
- This results in a significant dipole moment.
- **H₂O (Water)**:
- The O-H bonds are also polar, with an electronegativity difference of (3.5 - 2.1 = 1.4).
- The bent shape of the water molecule leads to a net dipole moment, making it quite polar.
- **H₂S (Hydrogen Sulfide)**:
- The S-H bonds have a smaller electronegativity difference (2.5 - 2.1 = 0.4), resulting in a less polar bond compared to HF and H₂O.
- The molecular geometry is also less effective in creating a net dipole moment compared to water.

4. **Comparing Dipole Moments**:
- Based on the analysis:
- HF has the highest dipole moment due to the strong electronegativity difference and linear geometry.
- H₂O has a significant dipole moment due to its bent shape and moderate electronegativity difference.
- H₂S has the lowest dipole moment due to the smaller electronegativity difference and less effective geometry.

5. **Conclusion**:
- The correct order of dipole moments is:
\[ \text{HF} > \text{H}_2\text{O} > \text{H}_2\text{S} \]