Which of the following liquids would exhibit the highest vapor pressure at 25.0°C?

• A. Ethanol (C2H5OH)
• B. Water (H2O)
• C. Diethyl ether (C4H10O)
• D. Glycerol (C3H8O3)

Answer: (C)

Verified step by step guidance

1. Understand that vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid at a given temperature. Liquids with weaker intermolecular forces have higher vapor pressures because their molecules escape more easily into the vapor phase.
2. Identify the types of intermolecular forces present in each liquid: Water (H2O) and Glycerol (C3H8O3) have strong hydrogen bonding due to multiple -OH groups; Ethanol (C2H5OH) has hydrogen bonding but fewer -OH groups; Diethyl ether (C4H10O) has dipole-dipole interactions and weaker London dispersion forces, but no hydrogen bonding between molecules.
3. Recall that stronger hydrogen bonding leads to lower vapor pressure because molecules are held more tightly in the liquid phase, while weaker forces lead to higher vapor pressure.
4. Compare the molecular structures and intermolecular forces: Glycerol has the strongest hydrogen bonding (lowest vapor pressure), followed by water, then ethanol, and finally diethyl ether with the weakest intermolecular forces.
5. Conclude that diethyl ether will have the highest vapor pressure at 25.0°C because it has the weakest intermolecular forces among the given liquids.