In the following, which substance will have highest boiling point

Options

A. `He`
B. `CsF`
C. `NH_3`
D. `CHCl_3`

Explanation

To determine which substance has the highest boiling point among the given options, we need to analyze the types of bonding and the nature of each substance.

### Step-by-Step Solution:

1. **Identify the Substances**: The substances mentioned are Helium (He), CSF (which is likely meant to be CS2, carbon disulfide), Ammonia (NH3), and CHCl3 (Chloroform).

2. **Determine the Type of Bonding**:
- **Helium (He)**: This is a noble gas and exists as individual atoms. It has very weak van der Waals forces (London dispersion forces) and does not form any bonds.
- **CS2 (Carbon Disulfide)**: This is a covalent compound. The forces holding CS2 together are primarily van der Waals forces.
- **Ammonia (NH3)**: This is a covalent compound that can form hydrogen bonds due to the presence of a nitrogen atom bonded to hydrogen. Hydrogen bonding is a strong intermolecular force.
- **CHCl3 (Chloroform)**: This is also a covalent compound. It has dipole-dipole interactions due to the polar C-Cl bonds, but it does not have hydrogen bonding like ammonia.

3. **Compare the Strength of Intermolecular Forces**:
- Helium has the weakest forces (van der Waals).
- CS2 has weak van der Waals forces.
- NH3 has strong hydrogen bonding, which significantly increases its boiling point.
- CHCl3 has dipole-dipole interactions, which are stronger than van der Waals but weaker than hydrogen bonds.

4. **Conclusion**: Among the substances, ammonia (NH3) has the strongest intermolecular forces due to hydrogen bonding. Therefore, it will have the highest boiling point compared to the other substances listed.

### Final Answer:
**Ammonia (NH3) will have the highest boiling point.**