Which of the following is a polar molecule ?

Options

A. Para dichiorobenzene
B. Carbon tetrachloride
C. Tetrachloroethene
D.

Answer

To determine which of the given molecules is a polar molecule, we will analyze each option step by step.

### Step 1: Analyze para-dichlorobenzene
- **Structure**: Para-dichlorobenzene has two chlorine atoms attached to a benzene ring at opposite positions (para position).
- **Electronegativity**: Chlorine is more electronegative than carbon, creating dipoles in the C-Cl bonds.
- **Dipole Moment**: The dipoles from the two C-Cl bonds are equal in magnitude but opposite in direction. Thus, they cancel each other out.
- **Conclusion**: Para-dichlorobenzene is a **non-polar molecule**.

### Step 2: Analyze carbon tetrachloride (CCl4)
- **Structure**: Carbon tetrachloride has a tetrahedral structure with four chlorine atoms surrounding a central carbon atom.
- **Electronegativity**: Each C-Cl bond has a dipole moment directed towards chlorine.
- **Dipole Moment**: The symmetrical tetrahedral shape means that the dipoles cancel each other out.
- **Conclusion**: Carbon tetrachloride is a **non-polar molecule**.

### Step 3: Analyze tetrachloroethene (C2Cl4)
- **Structure**: Tetrachloroethene has a double bond between two carbon atoms, with two chlorine atoms attached to each carbon.
- **Electronegativity**: Similar to carbon tetrachloride, each C-Cl bond has a dipole directed towards chlorine.
- **Dipole Moment**: The symmetrical arrangement of the chlorine atoms means that the dipoles cancel each other out.
- **Conclusion**: Tetrachloroethene is a **non-polar molecule**.

### Step 4: Analyze para-hydroxy phenol
- **Structure**: Para-hydroxy phenol has a hydroxyl group (-OH) attached to a benzene ring.
- **Electronegativity**: The O-H bond has a dipole directed towards oxygen.
- **Dipole Moment**: The presence of the hydroxyl group introduces an asymmetry in the molecule, and the dipole from the O-H bond does not cancel out with any other dipole.
- **Conclusion**: Para-hydroxy phenol is a **polar molecule**.

### Final Answer
Based on the analysis, the only polar molecule among the options is **para-hydroxy phenol**.

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