Question

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

Explanation:

Step1: Analyze intermolecular forces

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

Step2: Consider molecular size

London dispersion force increases with the increase in molecular size (number of electrons). The molecular formulas are:

• Liquid 1: \(CH_4\) (10 electrons)
• Liquid 2: \(CH_3CH_3\) (\(C_2H_6\), 18 electrons)
• Liquid 3: \(CH_3CH_2CH_3\) (\(C_3H_8\), 26 electrons)
• Liquid 4: \(CH_3CH_2CH_2CH_3\) (\(C_4H_{10}\), 34 electrons)

As the number of electrons (molecular size) increases, the strength of London dispersion force increases. Higher - strength intermolecular forces require more energy to break, so the boiling point increases.

Answer:

Liquid 4: \(CH_3CH_2CH_2CH_3\)