1. UNIT 6 SOLUTIONS AND GASES 6.6 What is vapor pressure and how do we use Table H? May 2, 2011 AIM: How does vapor pressure affect boiling point of a substance? DO NOW: 1. Which one of the following compounds would casue a lower freezing point? 2.0 M HCl or1.0M CaCl 2 2. A substance has an empirical formula of CH 2 and a molar mass of 56 grams per mole. The molecular formula for this compound is: (1) CH 2 (2)C 4 H 6 (3)C 4 H 8 (4)C 8 H 4

2. VAPOR PRESSURE Vapor pressure is the pressure exerted (given) by a vapor (gas) over the surface of a liquid When the vapor pressure equals the atmospheric pressure, BOILING occurs Therefore, BOILING POINT is the temperature in which the VAPOR PRESSURE = ATMOSPHERIC PRESSURE Vapor pressure of various substances in listed on TABLE H

3. ATMOSPHERIC PRESSURE = VAPOR PRESSURE @ BOILING POINT of a substance ATMOSPHERIC PRESSURE is 101.3kPa (Table A) KEY POINTS

5. What is the trend you are noticing?As temperature increases, the vapor pressure increases

6. LET’S TRY SOME 1.At 50 o C, which substance exerts the most vapor pressure? 2.What is the vapor pressure of water at 105 o C? 3.At what temperature does ethanol have a vapor pressure of 50kPa? 4.Find the boiling point of each liquid in o C. propane 120 o C 62 o C Propane: 56 o C Ethanol: 80 o C Water: 100 o C Ethanoic Acid: 118 o C

7. INDEPENDENT PRACTICE Complete the Independent Practice PLACE the lab in the CHEMICAL REACTIONS BIN YOU HAVE UNTIL WEDNESDAY, MAY 4,2011 to hand in the following: – labs – Test corrections HOMEWORK PACKET IS DUE FRIDAY, MAY 6, 2011