Which of the following compounds has the highest vapor pressure at 25 °C?

• A. CH3OH (methanol)
• B. C6H12O6 (glucose)
• C. CCl4 (carbon tetrachloride)
• D. H2O (water)

Answer: (C)

Verified step by step guidance

1. Recall that vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid at a given temperature. It depends on the strength of intermolecular forces: weaker intermolecular forces lead to higher vapor pressure.
2. Identify the types of intermolecular forces present in each compound: - CH3OH (methanol) has hydrogen bonding, dipole-dipole, and London dispersion forces. - C6H12O6 (glucose) has extensive hydrogen bonding due to multiple -OH groups. - CCl4 (carbon tetrachloride) has only London dispersion forces (nonpolar molecule). - H2O (water) has strong hydrogen bonding.
3. Compare the strength of intermolecular forces: hydrogen bonding > dipole-dipole > London dispersion forces. Since CCl4 only has London dispersion forces, it has the weakest intermolecular forces among the options.
4. Since weaker intermolecular forces correspond to higher vapor pressure, CCl4 will have the highest vapor pressure at 25 °C compared to the other compounds with stronger hydrogen bonding.
5. Therefore, the compound with the highest vapor pressure is the one with the weakest intermolecular forces, which is CCl4.