Which compound has the chemical formula CHCl₃ whose melting point is 209 K?

Chloroform

The correct answer is option 3. Chloroform.

Chloroform, with the chemical formula \(CHCl_3\), is an organic compound consisting of one carbon atom, one hydrogen atom, and three chlorine atoms. It is a colorless, volatile liquid with a sweet odor, and it is commonly used as a solvent and in various industrial applications.

Here is an explanation of the given information:

1. Chemical Formula:  The chemical formula \(CHCl_3\) indicates that chloroform contains one carbon atom \((C)\), one hydrogen atom \((H)\), and three chlorine atoms \((Cl)\). This formula represents the molecular structure of chloroform, where the carbon atom is bonded to one hydrogen atom and three chlorine atoms, resulting in a tetrahedral arrangement.

2. Melting Point:  The melting point of chloroform is given as 209 K. This indicates the temperature at which chloroform transitions from a solid to a liquid state under standard atmospheric pressure.

3. Properties:  Chloroform is a non-polar molecule due to its symmetrical molecular structure. It has a relatively low melting point compared to many other compounds, indicating its ability to transition easily between solid and liquid states. Chloroform is also volatile, meaning it can vaporize readily at room temperature.

4. Common Uses: Chloroform has been historically used as an anesthetic, although its use for this purpose has declined due to safety concerns. It is also utilized as a solvent in laboratories and in the production of various chemicals. Additionally, chloroform has applications in industry, such as in the manufacture of pharmaceuticals, pesticides, and plastics.

In summary, chloroform \((CHCl_3)\) is an organic compound with a molecular structure consisting of one carbon atom, one hydrogen atom, and three chlorine atoms. It has a melting point of 209 K and is commonly used as a solvent and in various industrial processes.