Which molecule is polar in each of the following pairs ?
(i) `HF, F_(2)" (ii) "CO_(2), H_(2)O`
(iii) `n_(2),NH_(3)" (iv) "CH_(4),CH_(3)Cl.`

Explanation

To determine which molecule is polar in each of the given pairs, we need to analyze the molecular structure and the electronegativity of the atoms involved. A molecule is considered polar if it has a net dipole moment, which occurs when there is a significant difference in electronegativity between the bonded atoms, leading to an uneven distribution of electron density.

### Step-by-Step Solution:

**(i) HF, F₂**
1. **HF (Hydrogen Fluoride)**:
- Hydrogen (H) has an electronegativity of about 2.1, while Fluorine (F) has an electronegativity of about 4.0.
- The difference in electronegativity (ΔEN) is significant (4.0 - 2.1 = 1.9), leading to a polar bond.
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