In which of the following substance will
hydrogen bond be strongest ?

Options

A. HCl
B. `H_(2) O `
C. HI
D. `H_(2) S`

Explanation

To determine in which substance the hydrogen bond will be strongest, we need to analyze the substances provided and their ability to form hydrogen bonds. Hydrogen bonds typically occur between hydrogen and highly electronegative atoms such as nitrogen (N), oxygen (O), or fluorine (F).

### Step-by-Step Solution:

1. **Identify the Substances**:
Let's assume the substances given are HCl, HI, H2SO4, and H2O.

2. **Understand Hydrogen Bonding**:
Hydrogen bonds form when hydrogen is covalently bonded to a highly electronegative atom (N, O, or F). The strength of the hydrogen bond increases with the electronegativity of the atom bonded to hydrogen.

3. **Electronegativity Values**:
- Fluorine (F): 4.0
- Oxygen (O): 3.5
- Nitrogen (N): 3.0
- Chlorine (Cl): 3.0
- Iodine (I): 2.5

4. **Evaluate Each Substance**:
- **HCl**: Contains Cl, which is not highly electronegative compared to O and F.
- **HI**: Contains I, which is the least electronegative among the halogens listed.
- **H2SO4**: Contains O, which can form hydrogen bonds, but the presence of sulfur may reduce the overall hydrogen bonding capability.
- **H2O**: Contains O, which is highly electronegative and can form strong hydrogen bonds with other water molecules.

5. **Compare the Strength of Hydrogen Bonds**:
- H2O can form extensive hydrogen bonding networks due to its two hydrogen atoms bonded to a highly electronegative oxygen atom.
- HCl and HI do not form strong hydrogen bonds due to lower electronegativity of Cl and I.
- H2SO4 can form hydrogen bonds but not as effectively as H2O due to the presence of sulfur.

6. **Conclusion**:
Based on the analysis, the strongest hydrogen bonds will be found in **H2O (water)**.

### Final Answer:
The substance in which the hydrogen bond will be strongest is **H2O (water)**.