1. Ch. 09: Liquids & Solids Vapor Pressure

2. Vapor = the gaseous state of a substance that has escaped from the liquid phase e.g., ½-filled cup of coffee:

3. vaporization = liquid is converted to its gas form (in open system, it continues to complete evaporation) liquid  vapor dynamic equilibrium: rate vaporization = rate condensation vapor (a gas) follows gas laws this chapter on closed system: dynamic equilibrium between liquid & vapor. Vapor Pressure

4. Vapor Pressure 9.1 Theory: When temperature rises, the vapor pressure of a liquid increases. (molecules have sufficient energy to break away from the surface of the liquid) When the vapor pressure = pressure above the liquid, the liquid boils. Special case: @1 atm, bp is called the normal boiling T b

5. Vapor Pressure 9.1

8. Vapor Pressure Vp = pressure exerted by the vapor over the liquid At equilibrium, Vp is independent of volume. The larger the volume, the more liquid that vaporizes ratio “n/V” remains constant, so: P = nRT/V does not changeuntil all of the liquid has vaporized, and Vp will be less that P equilibrium.

9. Vapor Pressure Example 9.1 A 2.0-L “cool mist” vaporizer adds moisture to dry air at 25 o C. The room is 12’ x 12’ x 8’. Vp H2O is 24 mmHg at 25 o C. (Assume density of 1.00 g/mL) (a) If the vaporizer runs until it is empty, what is the vapor pressure of the water in the room?