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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
5
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
6
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
7
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
9
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.
10
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
11
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
=×=
==⋅
=Δ
=
=Δ
12
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
13
Colligative Properties of SolutionsOsmotic pressure
Colligative Properties of SolutionsOsmotic pressure
Reverse Osmosis
14
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
15
Colloids
Colloids
Tyndall EffectTyndall Effect
1~1000 nm
Colloid: A suspension of tiny particles in some medium.
16
Colloids
net neutral net neutral
Repulsion prevents coagulation
Heat or Electrolyte causing coagulation of colloids
Colloids
Yellow River