Which of the following molecule forms linear polymeric structure due to H-bonding ?

Options

A. `NH_3`
B. `H_2O`
C. `HCl`
D. `HF`

Explanation

To determine which molecule forms a linear polymeric structure due to hydrogen bonding, we will analyze each of the given options: NH3, H2O, HCl, and HF.

### Step-by-Step Solution:

1. **Understanding Hydrogen Bonding**:
Hydrogen bonding occurs when a hydrogen atom covalently bonded to a highly electronegative atom (like N, O, or F) experiences an attraction to another electronegative atom. This results in a dipole-dipole interaction that can lead to the formation of polymers.

**Hint**: Recall that hydrogen bonds are stronger than typical dipole-dipole interactions but weaker than covalent bonds.

2. **Analyzing NH3 (Ammonia)**:
- Structure: NH3 has a trigonal pyramidal shape due to the presence of a lone pair on nitrogen.
- Hydrogen Bonding: NH3 can form hydrogen bonds, but the structure is not linear; it tends to form a network rather than a linear polymer.

**Hint**: Consider the shape of the molecule when determining if it can form a linear structure.

3. **Analyzing H2O (Water)**:
- Structure: H2O has a bent shape due to the two lone pairs on oxygen.
- Hydrogen Bonding: Water can form hydrogen bonds, but similar to NH3, it does not form a linear polymeric structure; it forms a tetrahedral arrangement.

**Hint**: Look at the angles between the bonds in the molecule to assess linearity.

4. **Analyzing HCl (Hydrochloric Acid)**:
- Structure: HCl is a simple diatomic molecule.
- Hydrogen Bonding: HCl does not exhibit significant hydrogen bonding because the electronegativity difference between H and Cl is not sufficient to create strong dipole-dipole interactions.

**Hint**: Check for the presence of significant electronegativity differences to determine hydrogen bonding capability.

5. **Analyzing HF (Hydrofluoric Acid)**:
- Structure: HF can form a linear arrangement when multiple HF molecules interact.
- Hydrogen Bonding: HF exhibits strong hydrogen bonding due to the high electronegativity of fluorine, leading to the formation of linear polymeric structures.

**Hint**: Consider how the strong hydrogen bonds can lead to a repeating linear pattern in the structure.

### Conclusion:
Based on the analysis, the molecule that forms a linear polymeric structure due to hydrogen bonding is **HF** (Hydrofluoric Acid).

**Final Answer**: D) HF