As pressure increases, the boiling point of a liquid in equilibrium with its vapor

As pressure increases, the boiling point of a liquid in equilibrium with its vapor

• A. Increases
• B. Decreases
• C. Remains the same
• D. Becomes undefined

Answer: (A)

Boiling happens when the vapor pressure of the liquid equals the surrounding pressure. If you raise the ambient pressure, the liquid must reach a higher temperature for its vapor pressure to match that larger pressure. So the boiling point moves upward with increasing pressure. This is why a pressure cooker lets water boil at temperatures above 100°C—the higher pressure requires more heat to generate enough vapor. If pressure drops, the boiling point falls. The key relation is that the boiling point is the temperature at which Pvap equals the external pressure, so increasing the external pressure raises that temperature.

Boiling happens when the vapor pressure of the liquid equals the surrounding pressure. If you raise the ambient pressure, the liquid must reach a higher temperature for its vapor pressure to match that larger pressure. So the boiling point moves upward with increasing pressure. This is why a pressure cooker lets water boil at temperatures above 100°C—the higher pressure requires more heat to generate enough vapor. If pressure drops, the boiling point falls. The key relation is that the boiling point is the temperature at which Pvap equals the external pressure, so increasing the external pressure raises that temperature.