Question

A chemist has three compounds of similar molecular weight, but with different dominant intermolecular forces. Select the compound that should have the lowest boiling point, based on the compound's dominant intermolecular force.

1) The compound in which covalent bonds are dominant
2) The compound in which dipole-dipole forces are dominant
3) The compound in which dispersion forces are dominant
4) The compound in which hydrogen bonding is dominant

Answer 1

The compound with dispersion forces as its dominant intermolecular force should have the lowest boiling point, as these are the weakest form of intermolecular forces when compared to dipole-dipole forces and hydrogen bonding.

Step-by-step explanation:

To determine which compound should have the lowest boiling point, we need to consider the dominant intermolecular forces present in each option. Here are the types of intermolecular forces listed in order from weakest to strongest: dispersion forces, dipole-dipole forces, hydrogen bonding. Covalent bonds are intramolecular forces, not intermolecular, so they are not considered here.

Since the question specifies 'dominant' intermolecular forces, we can exclude covalent bonds from the comparison. Among the options given:

• Dispersion forces are the weakest form of intermolecular forces.
  
• Dipole-dipole forces are stronger than dispersion forces.
  
• Hydrogen bonding is stronger than both dispersion and dipole-dipole forces.

Therefore, the compound with dispersion forces as its dominant intermolecular force should have the lowest boiling point.