Which substance has a dipole moment ?

Options

A. `C Cl_(4)`
B. `CH_(2)Cl_(2)`
C. `C_(2)Cl_(2)`
D. `C_(2)Cl_(4)`

Explanation

To determine which substance has a dipole moment, we need to analyze the molecular structure and polarity of the given substances. Here’s a step-by-step solution:

### Step 1: Understand Dipole Moment
A dipole moment arises in a molecule when there is a separation of charge due to differences in electronegativity between atoms, leading to a polar bond. If a molecule has a symmetrical structure, the dipole moments can cancel each other out, resulting in a net dipole moment of zero.

**Hint:** Remember that dipole moments are associated with polar molecules, which have an unequal distribution of electron density.

### Step 2: Analyze CCl4 (Carbon Tetrachloride)
CCl4 has a tetrahedral geometry. Although the C-Cl bonds are polar due to the electronegativity difference between carbon and chlorine, the symmetry of the tetrahedral shape causes the dipole moments to cancel out. Therefore, CCl4 has a dipole moment of zero.

**Hint:** Consider the molecular geometry and symmetry when evaluating dipole moments.

### Step 3: Analyze CH2Cl2 (Dichloromethane)
CH2Cl2 has a tetrahedral structure as well, but it is not symmetrical because it has two hydrogen atoms and two chlorine atoms. The electronegativity difference between chlorine and hydrogen means that the dipole moments do not cancel out completely, resulting in a net dipole moment. Therefore, CH2Cl2 has a dipole moment.

**Hint:** Look for asymmetry in the molecular structure to identify potential dipole moments.

### Step 4: Analyze C2H2 (Acetylene)
C2H2 has a linear structure. In this case, the molecule is symmetrical, and the dipole moments of the bonds cancel each other out, resulting in a dipole moment of zero.

**Hint:** Linear molecules with identical atoms on both ends usually have no dipole moment.

### Step 5: Analyze C2Cl4 (Tetrachloroethylene)
C2Cl4 also has a planar structure. Similar to C2H2, the symmetry in the arrangement of chlorine atoms leads to cancellation of dipole moments, resulting in a dipole moment of zero.

**Hint:** Check for planar structures with symmetrical arrangements to determine if they have a dipole moment.

### Conclusion
Among the substances analyzed, **CH2Cl2 (Dichloromethane)** is the only molecule that has a dipole moment due to its asymmetrical structure.

**Final Answer:** CH2Cl2 has a dipole moment.