In which of the following molecules, intermolecular attraction is purely London force?

Options

A. `CHCl_3`
B. `CH_2Cl_2`
C. `C``Cl_4`
D. `CH_3Cl`

Answer

To determine which of the given molecules has intermolecular attraction that is purely London force, we need to analyze the polarity of each molecule. The options are CHCl3, CH2Cl2, CCl4, and CH3Cl.

### Step-by-Step Solution:

1. **Identify the Structure of Each Molecule:**
- **CHCl3 (Chloroform):** This molecule has a tetrahedral structure with one hydrogen atom and three chlorine atoms. The electronegativity difference between H and Cl creates a dipole moment.
- **CH2Cl2 (Dichloromethane):** This molecule also has a tetrahedral structure with two hydrogen atoms and two chlorine atoms. The presence of chlorine atoms creates a net dipole moment.
- **CCl4 (Carbon Tetrachloride):** This molecule has a tetrahedral structure with four chlorine atoms. Although Cl is more electronegative than C, the symmetrical arrangement of the chlorine atoms results in a net dipole moment of zero.
- **CH3Cl (Methyl Chloride):** This molecule has a tetrahedral structure with three hydrogen atoms and one chlorine atom. The presence of chlorine creates a dipole moment.

2. **Determine the Polarity of Each Molecule:**
- **CHCl3:** Polar (has a dipole moment).
- **CH2Cl2:** Polar (has a dipole moment).
- **CCl4:** Non-polar (net dipole moment is zero).
- **CH3Cl:** Polar (has a dipole moment).

3. **Identify the Type of Intermolecular Forces:**
- **Polar Molecules (CHCl3, CH2Cl2, CH3Cl):** These molecules exhibit dipole-dipole interactions due to their dipole moments.
- **Non-Polar Molecule (CCl4):** This molecule exhibits London dispersion forces (also known as London forces), which are the only type of intermolecular force present in non-polar molecules.

4. **Conclusion:**
- The only molecule among the options that has purely London forces as its intermolecular attraction is **CCl4**.

### Final Answer:
**CCl4** (Carbon Tetrachloride) is the molecule where intermolecular attraction is purely London force.