Compare the ∆Hvap values for water, isopropyl alcohol, ether, and ammonia, and order them from lowest to highest. Explain the rank order based on intermolecular attractive forces.

Verified step by step guidance

1. Identify the substances involved: water, isopropyl alcohol, ether, and ammonia.
2. Understand that \( \Delta H_{\text{vap}} \) (enthalpy of vaporization) is the energy required to convert a liquid into a gas at its boiling point, which is influenced by the strength of intermolecular forces.
3. Recognize the types of intermolecular forces present in each substance: water has hydrogen bonding, isopropyl alcohol has hydrogen bonding but weaker than water, ether has dipole-dipole interactions and London dispersion forces, and ammonia has hydrogen bonding but weaker than water.
4. Compare the strength of these intermolecular forces: hydrogen bonds are generally stronger than dipole-dipole interactions and London dispersion forces, so substances with stronger hydrogen bonding will have higher \( \Delta H_{\text{vap}} \).
5. Order the substances from lowest to highest \( \Delta H_{\text{vap}} \) based on the strength of their intermolecular forces: ether (weakest forces), ammonia, isopropyl alcohol, and water (strongest forces).

Key Concepts

Enthalpy of Vaporization (∆Hvap)

Enthalpy of vaporization (∆Hvap) is the amount of energy required to convert a unit mass of a liquid into vapor at constant temperature and pressure. It reflects the strength of intermolecular forces within the liquid; higher ∆Hvap values indicate stronger forces that require more energy to overcome during the phase change from liquid to gas.

Intermolecular Forces

Intermolecular forces are the attractive forces between molecules that influence their physical properties, including boiling points and vaporization. The main types include hydrogen bonding, dipole-dipole interactions, and London dispersion forces. Stronger intermolecular forces lead to higher ∆Hvap values, as more energy is needed to separate the molecules.

Comparison of Liquids

When comparing the ∆Hvap values of different liquids, it is essential to consider their molecular structure and the types of intermolecular forces present. For instance, water exhibits strong hydrogen bonding, leading to a high ∆Hvap, while substances like ether, which primarily experience weaker London dispersion forces, will have lower ∆Hvap values. This comparison helps in ranking the liquids based on their vaporization energy requirements.