What is vapor pressure?

What is vapor pressure?

• A. The energy required to vaporize the liquid.
• B. The pressure of the liquid that pushes on the container walls.
• C. The atmospheric pressure needed to boil the liquid at room temperature.
• D. The pressure the vapor of a liquid exerts on its container when the vapor and liquid are in equilibrium.

Answer: (D)

Vapor pressure is the pressure the vapor phase exerts on the container walls (or on the liquid) when the liquid and its vapor are in equilibrium at a given temperature. In a closed system, molecules continuously evaporate from the liquid and condense back from the vapor, creating a steady pressure. As temperature rises, more molecules escape, so the vapor pressure increases. When this vapor pressure equals the surrounding atmospheric pressure, the liquid boils. This concept helps explain how volatile a substance is and why some chemicals can form hazardous vapor clouds in HazMat work.

Vapor pressure is the pressure the vapor phase exerts on the container walls (or on the liquid) when the liquid and its vapor are in equilibrium at a given temperature. In a closed system, molecules continuously evaporate from the liquid and condense back from the vapor, creating a steady pressure. As temperature rises, more molecules escape, so the vapor pressure increases. When this vapor pressure equals the surrounding atmospheric pressure, the liquid boils. This concept helps explain how volatile a substance is and why some chemicals can form hazardous vapor clouds in HazMat work.