What are the polarities of CH2Cl2 and CF2Cl2?
A.) Both are polar.
B.) Both are nonpolar.
C.) CH2Cl2 is nonpolar and CF2Cl2 is polar.
D.) CH2Cl2 is polar and CF2Cl2 is nonpolar.
The correct answer and explanation is:
The correct answer is: D.) CH2Cl2 is polar and CF2Cl2 is nonpolar.
Explanation:
The polarity of a molecule is determined by the distribution of electron density and the molecular geometry. Polar molecules have an uneven distribution of charge, whereas nonpolar molecules have a symmetric charge distribution.
- CH2Cl2 (Dichloromethane):
CH2Cl2 has a central carbon atom bonded to two hydrogen atoms and two chlorine atoms. The electronegativity difference between chlorine (Cl) and hydrogen (H) is significant, with chlorine being more electronegative. The chlorine atoms pull electron density towards themselves, creating partial negative charges on the chlorine atoms and partial positive charges on the hydrogen atoms. However, the molecule is asymmetric due to the different atoms around the central carbon. This leads to a net dipole moment, making CH2Cl2 a polar molecule. - CF2Cl2 (Dichlorodifluoromethane):
CF2Cl2 has a central carbon atom bonded to two fluorine atoms and two chlorine atoms. Fluorine is more electronegative than chlorine, and while fluorine pulls electron density towards itself, chlorine is still less electronegative. The molecule is symmetric because the fluorine atoms are opposite the chlorine atoms. The individual bond dipoles cancel each other out due to the symmetry of the molecule, resulting in no net dipole moment. Therefore, CF2Cl2 is a nonpolar molecule.
To summarize, CH2Cl2 is polar due to its asymmetric geometry and the unequal distribution of electron density, whereas CF2Cl2 is nonpolar because of its symmetric shape and the cancellation of bond dipoles.