Question

question 7 of 20 arrange the compounds by boiling point. answer bank pentane: h₃c - ch₂ - ch₂ - ch₂ - ch₃ propane: h₃c - ch₂ - ch₃ hexane: h₃c - ch₂ - ch₂ - ch₂ - ch₂ - ch₃

Explanation:

Step1: Consider intermolecular forces

For non - polar hydrocarbons like these, the main intermolecular force is London dispersion force. The strength of London dispersion force increases with the number of electrons (or molar mass).

Step2: Compare molar masses

Propane ($C_3H_8$) has a molar mass of approximately $3\times12 + 8\times1=44\ g/mol$. Pentane ($C_5H_{12}$) has a molar mass of approximately $5\times12+12\times1 = 72\ g/mol$. Hexane ($C_6H_{14}$) has a molar mass of approximately $6\times12 + 14\times1=86\ g/mol$.

Step3: Determine boiling - point order

Since the strength of London dispersion force is directly related to molar mass for these non - polar hydrocarbons, the compound with the highest molar mass has the highest boiling point and the one with the lowest molar mass has the lowest boiling point.

Answer:

Highest boiling point: hexane
Next: pentane
Lowest boiling point: propane