Chemistry 163B Colligative Properties Challenged Penpersonship Notes

Transcription

1 Chemistry 163 Colligative Properties Challenged Penpersonship Notes 1

2 colligative properties o solutions colligative One entry ound. Main Entry: col li ga tive Pronunciation: kä-lə- gā-tiv, kə- li-gə-tiv Function: adjective : depending on the number o particles (as molecules) and not on the nature o the particles <pressure is a colligative property> 2

3 quantitative treatment o colligative properties Handout #55 A. Freezing point depression. oiling Point Elevation C. Osmotic Pressure 3

4 quantitative treatment o colligative properties I. he pure solvent (component ) is originally in equilibrium in the two phases. II. Addition o solute (component A) lowers the chemical potential o the solvent in the solution phase III. emperature (reezing point depression, boiling point elevation) or pressure (osmotic pressure) must be altered to reestablish equilibrium between the solution and the pure solvent phase. IV. Obtain relationships between A or and change in or P. 4

5 reezing point depression (solid solution) I. pure solvent is originally in equilibrium in the two phases pure solid pure iquid at the normal melting s ( ) ( ) s ( ) ( ) ( ) 0 H ( ) H 0 melting or solid liquid usion 5

6 reezing point depression (solid solution) II. Still at, add solute A to solvent with resulting mole ractions A and solid ( ) ( ) s or the solvent () in solution: ( ln) ( solvent in so ) ( ) ( ) R ln s ( ) ( ) ( ) ( ) R ln s ( ) ( ) ( ) and ( ) 0 thus ( ) R ln 0 so the orward reacton (melting o the solid) would now occur spontaneously at 6

7 reezing point depression (solid solution) III. Alter temperature to restore equilibrium H 2 P d P H melting ( ) ( ) H P 2 P d melting 2 d old stu 7

8 reezing point depression (solid solution) III. Alter temperature to restore equilibrium (continued) ( ) ( ) H ( ) P P 0 since at 'new' equilibrium, ( ) 0 ( ) and ln. R rom eqn in II change in due to adding solute P H melting Rln d 2 P melting H melting Rln d d change in due to temperature change 8

9 reezing point lowering IV. Obtain relationships between and change in H melting Rln d 2 H Rln H ~ independent o 1 1 since lhs < 0 < (reezing point depression) melting melting H 1 1 melting exp (integratio n o eqn 9.31 E&R) R 9

10 reezing point lowering IV. Obtain relationships between and change in (cont) H 1 1 melting exp R R 1 1 ln H melting H melting H R ln melting (~ eqn 9.32 E&R) 10

11 Osmotic Pressure Equilibrium P 0 = 11

12 osmotic pressure (pure solvent solution [solvent + solute] ) I. pure solvent at P let is originally in equilibrium with pure solvent at P right ; i.e. P let =P right =P 0 pure iquid ( P, let) pure iquid ( P, right) at 'let' and 'right' reer to compartments separated by solute impermeable membrane ( P, let) ( P, right) 12

13 osmotic pressure (II add solute to let compartment) II. in let hand compartment add solute A to solvent with resulting mole ractions A and add solute to liquid in ' let ' compatment resulting in or solvent A ( P, let) ( P, let) R ln ( P, right) ( P, let) ( P, right) 0 0 so the solvent moves spontaneously let (i.e. diluting solution on let) right 13

14 osmotic pressure (III, alter pressure) III. alter Pressure: P let P 0 + to restore equilibrium solution (, P, let) pure solvent( P, right) P let V 0 0 P 0 0 P 0 0 P let d = V dp assuming solvent is incompressible ( V doesn't change with pressure at constant ) let, 0, let, P, P V let P P P P V P let

15 osmotic pressure (III, alter pressure, continued) let,, P P V let 0 0, ln P P R V let 0 0 right, P P let 0 0 P R ln V P 0 0 let right R ln V 15

16 osmotic pressure (a little more manipulation) R ln V or 1 and 1 ln(1 x) x or small x ( i. e. dilute solution, small) na A and na n n or dilute solution n n V A R ln 1 V AR V A nar nv n R A V n R solution solute A A 16

17 quantitative treatment o colligative properties Handout #55 Colligative Properties rom relationships or Chem 163 inal: 17

18 reverse osmosis 18

19 Reverse Osmosis 19

20 eect o osmosis on blood cells outside H O 2 2 outside H O inside H O 2 2 outside salt inside H O inside salt outside H O 2 2 outside salt inside H O inside salt outside H O 2 2 outside H O inside H O 2 2 outside salt inside H O inside salt 20

21 hyponatremia 21

22 End o Lecture