CHEM 135 1st Edition Lecture 6 Outline of Last Lecture I Review of Raoult s Law II Phase Diagram to indicate Freezing and Boiling point III Freezing point depression and boiling point elevation Outline of Current Lecture IV Review of freezing point depression and boiling point elevation a Examples V Osmosis VI Osmotic Pressure a Example Current Lecture Freezing point depression and boiling point elevation The freezing point of a solution is lower than the freezing point of the pure solvent Tf m Kf The boiling point of a solution is higher than the boiling point of the pure solvent Tb m Kb m molality of a solution in moles solute per kilogram solvent Kf Kb freezing point depression and boiling point elevation constants Ex Calculate the freezing point and boiling point of a solution containing 10 g of naphthalene C10H8 in 100 mL benzene d 0 877 g cm3 These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Equations needed Mass density volume moles m mass molar mass moles solute kg solvent T f m K f T f T f T f Given Mass of solute 10 g C10H8 Volume of solvent 100 mL benzene Density of solvent 0 877 g cm3 Tf Tb Strategy mass moles molality T f Tf Mass 0 877 g cm3 100 mL 87 7 g 0 0877 kg Moles Molality 10 g C 10 H 8 0 78 moles C 10 H 8 128 1 g mol 078 mol 89 m 0877 kg T f m K f T f T f T f T f 89 m 5 12 C m T f 5 5 C 4 56 C T f 4 56 C T f 0 94 C Follow the same steps using the boiling point formula T b m K b and T b T b T b to get a final boiling point of 82 35 C Osmosis is the flow of solvent from a solution of low concentration into a solution of high concentration Osmotic Pressure The amount of pressure needed to keep osmotic flow from taking place ie Osmotic pressure PREVENTS osmosis from occurring MRT osmotic pressure is directly proportional to the molarity of the solute M molarity moles L R 0 08206 atm L mol K
View Full Document
Unlocking...