Number of molecules having dipole moment among : `BF_(3), H_(2)O, NH_(3), H_(2)S, CO_(2)`, trans - 1, 2 - dichloroethene, `CH_(3)Cl, C Cl_(4)` HI` is

Explanation

To determine the number of molecules having a dipole moment among the given compounds, we will analyze each molecule one by one. A dipole moment exists in a molecule when there is an uneven distribution of electron density, leading to a polar bond or an overall polar molecule.

### Step-by-Step Solution:

1. **BF₃ (Boron Trifluoride)**:
- Structure: BF₃ is a trigonal planar molecule with three fluorine atoms symmetrically arranged around the boron atom.
- Dipole Moment: The dipole moments of the B-F bonds cancel each other out due to symmetry.
- Conclusion: **Dipole moment = 0** (not polar).

2. **H₂O (Water)**:
- Structure: H₂O has a bent shape due to the two lone pairs on oxygen.
- Dipole Moment: The dipole moments from the O-H bonds do not cancel out, resulting in a net dipole moment pointing towards the oxygen.
- Conclusion: **Dipole moment ≠ 0** (polar).

3. **NH₃ (Ammonia)**:
- Structure: NH₃ has a trigonal pyramidal shape with one lone pair on nitrogen.
- Dipole Moment: The dipole moments from the N-H bonds do not cancel out, resulting in a net dipole moment pointing towards the nitrogen.
- Conclusion: **Dipole moment ≠ 0** (polar).

4. **H₂S (Hydrogen Sulfide)**:
- Structure: H₂S has a bent shape similar to water but with two lone pairs on sulfur.
- Dipole Moment: The dipole moments from the S-H bonds do not cancel out, resulting in a net dipole moment pointing towards the sulfur.
- Conclusion: **Dipole moment ≠ 0** (polar).

5. **CO₂ (Carbon Dioxide)**:
- Structure: CO₂ is a linear molecule with two oxygen atoms on either side of the carbon atom.
- Dipole Moment: The dipole moments from the C=O bonds cancel each other out due to symmetry.
- Conclusion: **Dipole moment = 0** (not polar).

6. **Trans-1,2-Dichloroethene**:
- Structure: In trans-1,2-dichloroethene, the chlorine atoms are on opposite sides of the double bond.
- Dipole Moment: The dipole moments from the C-Cl bonds cancel out due to symmetry.
- Conclusion: **Dipole moment = 0** (not polar).

7. **CH₃Cl (Chloromethane)**:
- Structure: CH₃Cl has a tetrahedral shape with one chlorine atom and three hydrogen atoms.
- Dipole Moment: The dipole moment from the C-Cl bond does not cancel out with the C-H bonds.
- Conclusion: **Dipole moment ≠ 0** (polar).

8. **CCl₄ (Carbon Tetrachloride)**:
- Structure: CCl₄ is a tetrahedral molecule with four chlorine atoms symmetrically arranged around the carbon atom.
- Dipole Moment: The dipole moments from the C-Cl bonds cancel each other out due to symmetry.
- Conclusion: **Dipole moment = 0** (not polar).

9. **HI (Hydrogen Iodide)**:
- Structure: HI is a diatomic molecule with hydrogen and iodine.
- Dipole Moment: The dipole moment is directed from hydrogen to iodine due to the electronegativity difference.
- Conclusion: **Dipole moment ≠ 0** (polar).

### Summary of Results:
- Molecules with dipole moments (polar): H₂O, NH₃, H₂S, CH₃Cl, HI.
- Molecules without dipole moments (non-polar): BF₃, CO₂, trans-1,2-dichloroethene, CCl₄.

### Final Count:
- Total number of molecules with dipole moments = **5**.