Answer
$CO_{2}:$ Nonpolar, dispersion force
$CH_{3}Br:$ Polar, dipole-dipole forces
$CH_{3}OH:$ Polar, hydrogen bonding
$RbF:$ Ionic, Electrostatic ion-ion attractions
Increasing strength of intermolecular forces:
Dispersion force < dipole-dipole forces < hydrogen bonding < ion-ion attractions
Hence, increasing order of boiling point is:
$CO_{2} < CH_{3}Br < CH_{3}OH < RbF$
Work Step by Step
$CO_{2}:$ Nonpolar, dispersion force
$CH_{3}Br:$ Polar, dipole-dipole forces
$CH_{3}OH:$ Polar, hydrogen bonding
$RbF:$ Ionic, Electrostatic ion-ion attractions
Increasing strength of intermolecular forces:
Dispersion force < dipole-dipole forces < hydrogen bonding < ion-ion attractions
Hence, increasing order of boiling point is:
$CO_{2} < CH_{3}Br < CH_{3}OH < RbF$
