Which of the following lists ranks the molecules C2H6, C4H10, C6H14, and C8H18 in order of increasing strength of intermolecular forces?

• A. C2H6 < C4H10 < C6H14 < C8H18
• B. C4H10 < C2H6 < C8H18 < C6H14
• C. C6H14 < C2H6 < C4H10 < C8H18
• D. C8H18 < C6H14 < C4H10 < C2H6

Answer: (A)

Verified step by step guidance

1. Identify the type of intermolecular forces present in the molecules C2H6, C4H10, C6H14, and C8H18. Since all are nonpolar hydrocarbons (alkanes), the primary intermolecular forces are London dispersion forces.
2. Understand that London dispersion forces increase with the size (molar mass) and surface area of the molecule because larger molecules have more electrons and a greater ability to induce temporary dipoles.
3. Determine the relative molar masses of the molecules: C2H6 (ethane) < C4H10 (butane) < C6H14 (hexane) < C8H18 (octane).
4. Rank the molecules in order of increasing strength of intermolecular forces by arranging them from the smallest to the largest molar mass, since larger molecules have stronger London dispersion forces.
5. Conclude that the correct order of increasing intermolecular forces is: C2H6 < C4H10 < C6H14 < C8H18.