Question

Which of the following substances would you predict to have the highest Δhvap?

1) CH₃Cl
2) HCl
3) HOCH₂CH₂OH
4) CH₃CH₂OH
5) CH₃CH₂CH₂CH₃

Answer 1

HOCH2CH2OH (ethylene glycol) is predicted to have the highest heat of vaporization among the provided substances, as it can participate in extensive hydrogen bonding, requiring more energy to vaporize. so, option 3 is the correct answer.

Step-by-step explanation:

The student is asking which of the five given substances will have the highest heat of vaporization (ΔHvap). To predict the heat of vaporization, we must consider both the molecular mass and the type of intermolecular forces (IMFs) present in each substance.

1. CH3Cl - will have dipole-dipole interactions in addition to dispersion forces due to its molecular polarity.
2. HCl - also exhibits dipole-dipole interactions and dispersion forces.
3. HOCH2CH2OH (ethylene glycol) - has strong hydrogen bonding capabilities, significantly increasing its heat of vaporization.
4. CH3CH2OH (ethanol) - also has the ability to form hydrogen bonds but has a smaller molecular weight than ethylene glycol.
5. CH3CH2CH2CH3 (butane) - exhibits only dispersion forces since it is nonpolar.

Considering the intensity of IMFs and molecular size, HOCH2CH2OH would be predicted to have the highest ΔHvap due to its capacity for extensive hydrogen bonding which requires significant energy to overcome.