## Introductory Chemistry (5th Edition)

a. $O_{3}$ is polar molecule, polar bond exists in this molecule because of the difference in electronegativities of atoms in $O_{3}$. Thus dispersion force and dipole-dipole forces are present in $O_{3}$. b. $HBr$ is polar molecule, polar bond exists in this molecule because of difference in electronegativities of atoms in $HBr$. Thus dispersion force and dipole-dipole forces are present in $HBr$. c. In $CH_{3}OH$, all the bonds are nonpolar but some of all the bonds make the molecule polar. It also has hydrogen bonds. Hence dispersion forces, hydrogen bonds and dipole-dipole forces are present in the molecule. d. $I_{2}$ is a non polar molecule. Hence only dispersion forces are present.