Final answer:
The lower boiling point of CH₄ compared to CCl₄ is due to the stronger London dispersion forces in CCl₄ caused by its larger size and greater number of electrons. Option C is correct.
Step-by-step explanation:
The reason why CH₄ has a lower boiling point than CCl₄ is because of the difference in the strength of the intermolecular forces present in each compound. The correct explanation is that the London dispersion forces in carbon tetrachloride (CCl₄) are stronger than they are in methane (CH₄).
Methane is a small, nonpolar molecule and has only weak London dispersion forces due to its relatively low number of electrons and lack of a dipole moment. In contrast, the larger and heavier carbon tetrachloride molecules have more electrons and a higher capacity to develop temporary dipoles, resulting in significantly stronger London dispersion forces, which raise the boiling point of the substance.
The boiling point of a substance is determined by the strength of the intermolecular forces holding its molecules together. In the case of CH₄ (methane) and CCl₄ (carbon tetrachloride), the main intermolecular forces involved are dipole-dipole forces and London dispersion forces.
CCl₄ has stronger dipole-dipole forces than CH₄ because it has a dipole moment due to the polar C-Cl bonds. However, CH₄ has stronger London dispersion forces because it has more electrons, leading to greater temporary dipoles. Since London dispersion forces are generally weaker than dipole-dipole forces, CH₄ has a lower boiling point than CCl₄.