Which of the following are nonpolar molecules (polar bonds in a molecule effectively cancel each other out or all bonds in a molecule are relatively nonpolar)? Select the correct answer below:
a. CO
b. CO2
c. CH2O
d. CH4O
The Correct Answer and Explanation is :
The correct answer is b. CO2 (Carbon Dioxide).
Explanation:
To determine which of these molecules are nonpolar, we need to evaluate both the polarity of the individual bonds and the geometry (shape) of the molecule as a whole.
- CO (Carbon Monoxide):
- Bond polarity: The bond between carbon and oxygen is polar due to the significant difference in electronegativity between carbon and oxygen. Oxygen is more electronegative than carbon, so the bonding electrons are pulled toward oxygen.
- Molecular geometry: CO is a linear molecule. The polarity of the bond is not canceled out by symmetry in this case, so CO is a polar molecule.
- CO2 (Carbon Dioxide):
- Bond polarity: The bonds between carbon and oxygen are polar. Oxygen is more electronegative than carbon, creating a dipole in each C=O bond.
- Molecular geometry: CO2 has a linear geometry (O=C=O). Despite the individual C=O bonds being polar, the molecule’s linear shape causes the dipoles to cancel each other out. As a result, CO2 is a nonpolar molecule.
- CH2O (Formaldehyde):
- Bond polarity: The bonds between carbon and hydrogen are relatively nonpolar, but the C=O bond is polar.
- Molecular geometry: Formaldehyde has a trigonal planar geometry. The C=O bond is polar and does not cancel out with the C-H bonds. Therefore, CH2O is a polar molecule.
- CH4O (Methanol):
- Bond polarity: The O-H bond is polar, and the C-H bonds are relatively nonpolar.
- Molecular geometry: Methanol has a tetrahedral geometry. The molecule is not symmetric, and the O-H bond creates an overall dipole. Hence, CH4O is a polar molecule.
Conclusion:
- CO2 is the nonpolar molecule because its linear shape causes the bond dipoles to cancel out.