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1 Chapter 11. Properties of Solutions Solutions Homogeneous Mixture

Zumdahl chap 11 2009.ppt [호환 모드] - KNUbh.knu.ac.kr/~leehi/index.files/Zumdahl_chap_11_2010.pdf · 5 Factors affecting solubility Pressure effect little effect on the solubility

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Chapter 11. Properties of Solutions

Solutions

Homogeneous Mixture

2

Solution Composition

Acid-Base reaction1 th tit f id b th t

Equivalent

(mol) solute of moles(M)Molarity = 1 eq: the quantity of acid or base that can furnish or accept 1 mole of H+.

solution of mols totalA solute of moles )(fraction Mole

100%solution of masssolute of masspercent (weight) Mass

(L)solution ofliter (M)Molarity

A =

×=

=

χ

Redox reaction1 eq: the quantity of oxidant or reductant that can accept or furnish 1 mole of electrons.

MnO4- + 5 e- + 8 H+ --> Mn2

+ + 4H2O1 mole of MnO4

- --> 5 eq of MnO4-

solution ofliter solute of sequivalent ofnumber (N)Normality

(kg)solvent of kilogram(mol) solute of moles (m)Molality

=

=

Solution Composition

(mol) solute of moles(M)Molarity =

Ex) 3.75 M H2SO4 solution (electrolyte in Pb battery), d=1.230 g/mL --> mass percent, molality, normality?

solution of mols totalA solute of moles )(fraction Mole

100%solution of masssolute of masspercent (weight) Mass

(L)solution ofliter (M)Molarity

A =

×=

=

χ

mass percentsolution mass in 1 L solution = 1230 gsolute mass in 1 L solution = 3.75 mol x 98.1 g/mol = 368 gmass percent = 368g/1230g = 0.299 = 29.9 %

molalitysolvent mass in 1 L solution = 1230 g - 368 g = 862 g moles of solute in 1 L solution = 3.75 mol

l li 3 75 l/862 3 75 l/0 862 k

solution ofliter solute of sequivalent ofnumber (N)Normality

(kg)solvent of kilogram(mol) solute of moles (m)Molality

=

=molality = 3.75 mol/862 g = 3.75 mol/0. 862 kg= 4.35 mol/kg = 4.35 m

normalitysolute eq in 1 L solution = 3.75 mol/(2 eq/mol)= 7.50 eqnormality = 7.50 eq/L = 7.50 N

3

Energies of Solution Formation

Heat of solution (ΔHsoln = ΔH1 + ΔH2 + ΔH3)

Energies of Solution Formation

Ethanol - Water

Oil-Water

4

Energies of Solution Formation

NaCl in Water

NaCl(s) Na+(g) + Cl-(g) ΔH1 = 786 kJ/mol

H2O(l) + Na+(g) + Cl-(g) Na+(aq) + Cl-(aq)

H H H 783 kJ/ l

ΔG = ΔH - TΔS

ΔH2 + ΔH3 = ΔHhyd= -783 kJ/mol

ΔH1 ΔH2 + ΔH3 = ΔHsoln= 3 kJ/mol

not much favorable, then what happens?

heat of hydration

Factors affecting solubilityStructure effect Pressure effect Temperature effect

it i A vitamin Cvitamin A

vitamin D1

vitamin C

hydrophobic hydrophilic

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Factors affecting solubilityPressure effect

little effect on the solubility of solids or liquidsfor gas, solubility ↑ as P ↑

equilibrium new equilibrium

Factors affecting solubilityPressure effect

H ' L Th t f di l d i l ti i di tl ti l

CC = = kPkP

Henry's Law: The amount of a gas dissolved in a solution is directly proportional to the pressure of the gas above the solution. P = partial pressure of gaseous solute above the solutionC = concentration of dissolved gask = a constant

Ex) Before opening, PCO2 = 5 atm inside of the bottle. CCO2 in the beer solution before and after opening ? (PCO2(air) = 4.0 x 10-4 atm, kCO2 = 3.1 x 10-2 mol/L·atm at 25oC)

Before opening, CCO2 = kCO2PCO2 = (3.1 x 10-2 mol/L·atm)x(5atm) = 0.16 mol/LAfter opening, CCO2 = kCO2PCO2(air) = (3.1 x 10-2 mol/L·atm)x(4.0x10-4atm) = 1.2x10-5 mol/L

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Factors affecting solubilityTemperature effect (for aqueous solutions)

T ↑, speed of dissolving ↑

Solid

↑, p g ↑But solubility depends on the substance to be dissolved.

difficult to predict.empirical

Factors affecting solubilityTemperature effect (for aqueous solutions)

T ↑, solubility ↓ in water.

Gas

↑, yT ↑, solubility ↑ in most nonaqueous solvents.

1 atm

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Factors affecting solubilityTemperature effect (for aqueous solutions)

thermal pollution

Vapor Pressures of Solutions

non-volatile solute

Pvap(pure water) > Pvap(solution)if

to make equilibrium

Nonvolatile solute lowers the vapor pressure of a solvent.

8

Vapor Pressures of Solutions

number of solvent molecules at the surface ↓Pvap ↓

Nonvolatile Solute

Psoln = χsolventPosolvent

Raoult’s Law: The presence of a nonvolatile solute lowers the vapor pressure of a solvent.Psoln = vapor pressure of the solution, χsolvent = mole fraction of the solventPsolvent = vapor pressure of the pure solvent

Vapor Pressures of Solutions

Liquid (volatile)-liquid (volatile) solution(volatile) solution

χA + χB = 1

Ideal solution: A liquid-liquid solution that obeys Raoult's law.

Ptotal = PA+PB = χAPoA+χBP

oB

CH3

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Vapor Pressures of SolutionsNonideal solutions: liquid-liquid solution not-obeying Raoult's law

Ptotal >χAP

oA+χBP

oB

Ptotal <χAP

oA+χBP

oBχA A χB B

CH3 CH2

OH

O

CH3

CH3

H O

H

δ- δ+

CH3

CH2CH2

CH2CH2

CH3

Colligative Properties of Solutions

Boiling-Point Elevation Freezing-Point Depression Osmotic Pressure

Colligative properties: Properties depend only on the number, not on the identity, of the solute particles in an ideal solution.

g g p

normal boiling point:temperature where the vapor pressure is equal to 1 atm.

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Colligative Properties of SolutionsBoiling-Point Elevation Freezing-Point Depression

Nonvolatile Solute

ΔTb = kbmsolutekb : molal boiling-point elevation constant of solvent

msolute: molality of soluteΔTf = kfmsolute

kf : molal freezing-point depression constant of solvent

Colligative Properties of SolutionsBoiling-Point Elevation Freezing-Point Depression

Nonvolatile Solute

ΔTb = kbmsolutekb : molal boiling-point elevation constant of solvent

msolute: molality of soluteΔTf = kfmsolute

kf : molal freezing-point depression constant of solvent

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Colligative Properties of SolutionsBoiling-Point Elevation Freezing-Point Depression

1 atm, 0 oC1 atm, 100 oC

Ice Water Ice WaterIce Water Ice Water

Tf ↓Steam Water Steam Water

Tb ↑

Colligative Properties of SolutionsBoiling-Point Elevation Freezing-Point Depression

Ex) Mass of ethylen glycol (C2H6O2) to make antifreeze with Tf = -23.3 oC in 10.0 L water?(kf = 1.86 oC·kg/mol)

gmolgmolmass

kgmolkgmolmolkgC

CkT

m

mkT

solute

o

o

f

fsolute

soluteff

7760/1.62125

10/125/5.12/86.1

3.23

=×=

==⋅

=

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Colligative Properties of SolutionsOsmotic pressure

more

semipermiable

more

Osmosis: The flow of solvent into the solution through the semipermeable membrane.g p

Osmotic Pressure: The excess hydrostatic pressure on the solution compared to the pure solvent.

Π = MRT M: molarity of solution

Colligative Properties of SolutionsOsmotic pressure

semipermiable membrane: through which only solvent molecules are permeable.

NORMAL RED BLOOD CELLS:NORMAL RED BLOOD CELLS:0.9% NaCl Isotonic Solution

RED BLOOD CELLS - CRENATION: 20.0% NaCl Hypertonic Solution

allowing transfer of both solvent molecules and small solute molecules and ions.

RED BLOOD CELLS - HEMOLYSIS: Distilled Water Hypotonic Solution

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Colligative Properties of SolutionsOsmotic pressure

Colligative Properties of SolutionsOsmotic pressure

Reverse Osmosis

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Colligative Properties of SolutionsColligative Properties of Electrolyte Solutions

solutionin particlesofmolesidissolvedsolutesofmoles

p=i

van't Hoff factor

Π = iMRTΔT = imsolutek

Colligative Properties of SolutionsColligative Properties of Electrolyte Solutions

Ex) 0.1 M Fe(NH4)2(SO4)2 solution, Π=10.8 atm --> i (25 oC)?

Fe(NH4)2(SO4)2 (aq) --> Fe2+ (aq) + 2NH4+ + 2 SO4

2-

expected i = 5

Π = iMRT

i = Π/MRT = (10.8 atm)/(0.10 mol/L)·(0.08206 L·atm/K·mol)·(298K) = 4.4

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Colloids

Colloids

Tyndall EffectTyndall Effect

1~1000 nm

Colloid: A suspension of tiny particles in some medium.

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Colloids

net neutral net neutral

Repulsion prevents coagulation

Heat or Electrolyte causing coagulation of colloids

Colloids

Yellow River

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ColloidsYellow River Delta, Yesterday and Today

Yellow River Delta, Yesterday and Today

Colloids

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