Solutions dilute Concentration units M molarity moles of

Solutions (dilute) Concentration units M = molarity moles of solute L of solution X = mol fraction mol of solute mol solute + mol solvent weight % mass of solute x 100 mass of solution m = molality moles of solute kg solvent

Henry’s Law pressure and solubility of gases O 2 k. H (water) 4. 34 x 104 atm N 2 8. 57 x 104 atm P = k. H X 1 atm = 8. 57 x 104 Xnitrogen [N 2] = 0. 65 x 10 -3 M 8. 9 atm = 8. 57 x 104 Xnitrogen [N 2] = 5. 8 x 10 -3 M if gases react with water CO 2 (g) + H 2 O H 2 CO 3 (aq) 4 O 2(g) + Hb Hb(O 2)4 NH 3 (g) + H 2 O NH 4+ (aq) + OH- (aq)

Vapor Pressure of Solutions vapor pressure of liquid evaporation condensation water 25 o. C Pwater = 23. 76 torr add 162 g sugar to 1. 0 L Psolution = 23. 57 torr Raoult’s Law Psolution = Posolvent Xsolvent pure solvent solute qualitatively fewer solvent molecules at surface

Raoult’s Law Psolution = Posolvent Xsolvent water 25 o. C Pwater = 23. 76 torr add 162 g sugar to 1. 0 L Xsolvent = Psolution = 23. 57 torr 0. 992 = 55. 51 + x x = 0. 44 molsugar Psolution = 23. 57 Posolvent 23. 76 Xsolvent = 0. 992 = nwater + nsugar 1. 0 L = 1000 g = 55. 51 mol 18. 02 g/mol 162 g sugar = 365 g/mol molecular weight of sucrose 0. 44 molsugar

Powater > Psolution = Powater Xwater

Raoult’s Law two volatile components Psolution = Po. A XA + Po. B XB gas = PA + PB liquid X B = PB = 15. 0 =. 36 PA + PB 32. 6 Daltons Law mix 80 mol A + 20 mol B What is Ptot ? Ptot = 17. 6 + 15. 0 = 32. 6 PA (torr) 75 Ptotal PB (torr) 22 1 XA 0 0 XB 1 Po. A= 22 XA = 80 /(80+20) = 0. 8 Po. B= 75 XB = 20/(80+20)= 0. 2

Fractional Distillation Potoluene = 22 Xtoluene =. 64 Xtoluene = 0. 8 Pobenzene = 75 Xbenzene =. 36 Xbenzene = 0. 2 Xtoluene Ptoluene (torr) 75 Ptotal Potoluene = 22 =. 34 Xtoluene =. 64 Pobenzene = 75 Xbenzene =. 66 Xbenzene =. 36 Pbenzene (torr) 22 1 Xtoluene 0 0 Xbenzene 1 Ideal solution

Raoult’s Law two volatile components Ideal solution LDF benzene LDF toluene higher vapor pressure LDF

Raoult’s Law acetone two volatile components water non-ideal solution H-bonding IMFsoln > IMFcomponents H-bond dipole-dipole Vsoln < Vacetone + Vwater P. E. soln increase K. E. soln increase decrease Tsolution > Tcomponents

Raoult’s Law two volatile components acetone water non-ideal solution negative deviation mixing exothermic Hmixing < 0 229 Poacetone Powater 23. 8 Xacetone Xwater

Raoult’s Law two volatile components CHCl 3 non-ideal solution dipole-dipole C 2 H 5 OH dipole-dipole positive deviation mixing endothermic H-bond Hmixing > 0 194 Poethanol Pochloroform 59. 0 Xchloroform Xethanol

Raoult’s Law Psolution = Posolvent Xsolvent lower P of solution raise boiling point of solution Tb = b. p. solution - b. p. solvent Tb = KB molal boiling-point = 0. 51 kg K/mol elevation constant = 0. 34 mol m molality of solution (mol solute/kg solvent) 0. 500 kg 20 g Na. Cl 500 m. L water What is Tb? Tb = 0. 51 kg K/mol x 0. 68 = 0. 35 K 100. 79 o. C Na. Cl electrolyte 2 mol particles / mol formula Colligative Property

Colligative Property Tb = KB m i i = moles of particles moles of solute i non-electrolyte glucose electrolyte Na. Cl Fe. Cl 3 HCl i (expected) (observed) 1 1 2 4 2 1. 9 3. 4 1. 9

Freezing point depression Tf = KF m i 0. 05 m Na. NO 3 KF molal freezing-point depression constant m molality of solution (mol solute/kg solvent) 0. 075 m Cu. SO 4 0. 06 m (NH 4)2 SO 4 0. 14 m sucrose

Osmotic Pressure cellular biology molecules across membranes cell membrane = gh permeable to water impermeable to protein, etc. = MRT most accurate of colligative properties