Questions: You may have observed that rubbing alcohol (isopropyl alcohol) evaporates more easily than water. This indicates that the normal boiling point of water is higher than that of rubbing alcohol. Which of these two substances possesses stronger attractive forces between molecules? Briefly explain your answer.

You may have observed that rubbing alcohol (isopropyl alcohol) evaporates more easily than water. This indicates that the normal boiling point of water is higher than that of rubbing alcohol. Which of these two substances possesses stronger attractive forces between molecules? Briefly explain your answer.

Transcript text: You may have observed that rubbing alcohol (isopropyl alcohol) evaporates more easily than water. This indicates that the normal boiling point of water is higher than that of rubbing alcohol. Which of these two substances possesses stronger attractive forces between molecules? Briefly explain your answer.

Solution

Solution Steps

Step 1: Understanding Boiling Point and Intermolecular Forces

The boiling point of a substance is the temperature at which its vapor pressure equals the external pressure. A higher boiling point indicates that more energy is required to break the intermolecular forces holding the molecules together in the liquid phase.

Step 2: Comparing Boiling Points

Water has a normal boiling point of 100°C, while isopropyl alcohol (rubbing alcohol) has a normal boiling point of approximately 82.6°C. Since water has a higher boiling point, it requires more energy to transition from liquid to gas.

Step 3: Inferring Intermolecular Forces

Stronger intermolecular forces result in a higher boiling point because more energy is needed to overcome these forces. Therefore, the substance with the higher boiling point (water) must have stronger intermolecular forces compared to the substance with the lower boiling point (isopropyl alcohol).