Arrange the following molecules from most to least polar.
`underset("I")(CH_(4))underset("II")(CF_(2)Cl_(2))underset("III")(CF_(2)H_(2))underset("IV")("CCl"_(4))underset("V")(CH_(2)Cl_(2))`

Options

A. III gt V gt II gt I = IV
B. II gt IV gt III gt IV gt I
C. III gt II gt V gt IV gt I
D. V gt III gt II gt IV gt I

Answer

To determine the polarity of the given molecules (CH₄, CF₂Cl₂, CF₂H₂, CCl₄, and CH₂Cl₂), we will analyze their structures and the electronegativities of the atoms involved. The polarity of a molecule is influenced by the presence of polar bonds and the molecular geometry.

### Step-by-Step Solution:

1. **Identify the Electronegativity of Atoms:**
- Carbon (C) has an electronegativity of about 2.5.
- Fluorine (F) has an electronegativity of about 4.0.
- Chlorine (Cl) has an electronegativity of about 3.0.
- Hydrogen (H) has an electronegativity of about 2.1.

2. **Analyze Each Molecule:**
- **CH₄ (Methane):**
- Tetrahedral geometry with C-H bonds.
- The dipole moments cancel out due to symmetry.
- **Polarity:** Nonpolar (Dipole moment = 0).

- **CCl₄ (Carbon Tetrachloride):**
- Tetrahedral geometry with C-Cl bonds.
- The dipole moments cancel out due to symmetry.
- **Polarity:** Nonpolar (Dipole moment = 0).

- **CF₂Cl₂ (Dichlorodifluoromethane):**
- Tetrahedral geometry with two F and two Cl atoms.
- F is more electronegative than Cl, leading to a net dipole moment.
- **Polarity:** Polar (Dipole moment > 0).

- **CF₂H₂ (Difluoromethane):**
- Tetrahedral geometry with two F and two H atoms.
- The electronegativity difference between F and H creates a significant dipole moment.
- **Polarity:** Polar (Dipole moment > CF₂Cl₂).

- **CH₂Cl₂ (Dichloromethane):**
- Tetrahedral geometry with two Cl and two H atoms.
- The electronegativity difference between Cl and H creates a dipole moment.
- **Polarity:** Polar (Dipole moment < CF₂H₂ but > CF₂Cl₂).

3. **Rank the Molecules by Polarity:**
- Most Polar: **CF₂H₂**
- Second: **CH₂Cl₂**
- Third: **CF₂Cl₂**
- Least Polar: **CH₄** and **CCl₄** (both nonpolar)

4. **Final Arrangement from Most to Least Polar:**
- **CF₂H₂ > CH₂Cl₂ > CF₂Cl₂ > CH₄ = CCl₄**

### Final Answer:
The order of polarity from most to least polar is:
**CF₂H₂ (III) > CH₂Cl₂ (V) > CF₂Cl₂ (II) > CH₄ (I) = CCl₄ (IV)**