Question

storyline 1 exam
which of the molecules has the highest boiling point?
liquid 4: ch₃ch₂ch₂ch₃
liquid 3: ch₃ch₂ch₃
liquid 2: ch₃ch₃
liquid 1: ch₄

Explanation:

Step1: Analyze intermolecular forces

All these are non - polar hydrocarbons. The main intermolecular force is London dispersion force.

Step2: Consider molecular size

The strength of London dispersion force increases with the increase in molecular size (number of electrons). Larger molecules have more electrons, leading to stronger temporary dipoles.

• Liquid 1 ($CH_4$) has the smallest molecular size.
• Liquid 2 ($CH_3CH_3$) is larger than Liquid 1.
• Liquid 3 ($CH_3CH_2CH_3$) is larger than Liquid 2.
• Liquid 4 ($CH_3CH_2CH_2CH_3$) has the largest molecular size among them.

Since stronger intermolecular forces (London dispersion force in this case) require more energy to break the intermolecular interactions and convert the liquid to gas (higher boiling point), the molecule with the largest size (Liquid 4) will have the highest boiling point.

Answer:

Liquid 4: $CH_3CH_2CH_2CH_3$