Exercises
Exercise 1. Indicate if SiCl4 and SCl4 are polar or nonpolar.
First draw the Lewis structures.
The shape of SiCl4 is tetrahedral. There are 4 bonds, all identical, with zero lone pairs on Si. This molecule is nonpolar. The electron pair geometry of SCl4 is trigonal bipyramidal, but there are 4 bonds and one lone pair in an equatorial position. This molecule is polar.
Exercise 2. Explain why CO2 has a zero dipole moment while SO2 has a dipole moment of 1.63 D.
First, draw the Lewis structures.
CO2 has a linear shape with 2 identical bonds. The molecule is nonpolar. SO2 has two identical bonds, but there is a lone pair of electrons on the sulfur atom. This molecule is bent and it is polar due to the lone pair of electrons.
Exercise 3. Which of the following would have a nonzero dipole moment? Show the dipole direction for each polar molecule.
This molecule is polar due to the electronegative nitrogen and only one carbon atom.
b) PCl3
This molecule is polar due to the lone pair of electrons.
c) XeF2
d) BF3
Both XeF2 and BF3 are nonpolar.
XeF2 has a trigonal bipyrmadidal electron pair geometry. There are three lone pairs in equatorial positions. The molecular shape is linear. Because there are three lone pairs in the equatorial positions, there is no net dipole moment. The molecule is nonpolar. BF3 has a trigonal planar electron pair and molecular geometry. The bonds point to the corners of an equilateral triangle, and the dipoles cancel out. The molecule is nonpolar.
Exercise 4. Does H2C=CHCl have a dipole moment? If so, draw the direction of the dipole moment.
Yes, the molecule is polar. The C-Cl bond is polar and there are only 2 carbon atoms, well below the 4 carbon atoms.
