Question 3.16: Polarity of Covalent Molecules Which of these molecules are ...
Polarity of Covalent Molecules
Which of these molecules are polar? Show the direction of the molecular dipole by using an arrow with a crossed tail.
(a) \text{CH}_{2}\text{Cl}_{2} (b) \text{CH}_{2}\text{O} (c) \text{C}_{2}\text{H}_{2}
Strategy
To determine whether a molecule is polar, first determine if it has polar bonds, and if it does, determine if the centers of positive and negative charge lie at the same or different places within the molecule. If they lie at the same place, the molecule is nonpolar; if they lie at different places, the molecule is polar.
Both dichloromethane, \text{CH}_{2}\text{Cl}_{2} , and formaldehyde, \text{CH}_{2}\text{O}, have polar bonds and because of their geometry are polar molecules. Because acetylene, \text{C}_{2}\text{H}_{2} , contains no polar bonds, it is a nonpolar molecule.
■ Quick Check 3.16
Which of these molecules are polar? Show the direction of the molecular dipole by using an arrow with a crossed tail.
(a) \text{H}_{2}\text{S} (b) HCN (c) \text{C}_{2}\text{H}_{6}