Which statement best compares the melting point of butane (C_4H_{10}) with that of octane (C_8H_{18})?

• A. Butane (C_4H_{10}) has a higher melting point than octane (C_8H_{18}) because it is a smaller molecule.
• B. Octane (C_8H_{18}) has a lower melting point than butane (C_4H_{10}) because longer chains decrease melting point.
• C. Octane (C_8H_{18}) has a higher melting point than butane (C_4H_{10}) because it has a larger molecular mass and stronger London dispersion forces.
• D. Both butane and octane have the same melting point because they are both hydrocarbons.

Answer: (C)

Verified step by step guidance

1. Understand that melting point is influenced by the strength of intermolecular forces between molecules in the solid phase.
2. Recognize that both butane (C_4H_{10}) and octane (C_8H_{18}) are nonpolar hydrocarbons, so the primary intermolecular forces present are London dispersion forces.
3. Recall that London dispersion forces increase with increasing molecular size and molecular mass because larger molecules have more electrons and a more easily polarizable electron cloud.
4. Compare the molecular sizes: octane has a longer carbon chain and greater molecular mass than butane, which leads to stronger London dispersion forces in octane.
5. Conclude that stronger intermolecular forces in octane result in a higher melting point compared to butane.