Physical Properties of SolutionsChapter 13
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
용액의 물리적 성질
• 13.1 용액의 유형• 13.2 용해과정의 분자적 고찰• 13.3 농도 단위• 13.4 용해도에 미치는 온도의 영향• 13.5 기체의 용해도에 미치는 압력의 영향• 13.6 총괄성
A solution is a homogenous mixture. 균일 혼합물
The solute is(are) the substance(s) present in the smaller amount(s)
The solvent is the substance present in the larger amount
A saturated solution contains the maximum amount of a solute that will dissolve in a given solvent at a specific temperature.
An unsaturated solution contains less solute than the solvent has the capacity to dissolve at a specific temperature.
A supersaturated solution contains more solute than is present in a saturated solution at a specific temperature.
Sodium acetate crystals rapidly form when a seed crystal isadded to a supersaturated solution of sodium acetate.
Three types of interactions in the solution process:• solvent-solvent interaction• solute-solute interaction• solvent-solute interaction
Hsoln = H1 + H2 + H3
“like dissolves like”
Two substances with similar intermolecular forces are likely to be soluble in each other.
• non-polar molecules are soluble in non-polar solvents
CCl4 in C6H6
• polar molecules are soluble in polar solvents
C2H5OH in H2O
• ionic compounds are more soluble in polar solvents
NaCl in H2O or NH3 (l)
용액 - 균일 혼합물 조성비 - 농도
물리적 표현법• 질량 백분율
화학적 표현법 ( 단위당 화학량 (number))
• 몰농도 (M) mol/Lsolution
• 몰랄농도 (m) mol/kgsolvent
• 몰분율 (x) mol/moltotal
Concentration UnitsThe concentration of a solution is the amount of solute present in a given quantity of solvent or solution.
Percent by Mass
% by mass = x 100%mass of solutemass of solute + mass of solvent
= x 100%mass of solutemass of solution
Mole Fraction (X)
XA = moles of A
sum of moles of all components
Concentration Units Continued
M =moles of solute
liters of solution
Molarity (M)
Molality (m)
m =moles of solute
mass of solvent (kg)
What is the molality of a 5.86 M ethanol (C2H5OH) solution whose density is 0.927 g/mL?
m =moles of solute
mass of solvent (kg)M =
moles of solute
liters of solution
Assume 1 L of solution:5.86 moles ethanol = 270 g ethanol927 g of solution (1000 mL x 0.927 g/mL)
mass of solvent = mass of solution – mass of solute
= 927 g – 270 g = 657 g = 0.657 kg
m =moles of solute
mass of solvent (kg)=
5.86 moles C2H5OH
0.657 kg solvent= 8.92 m
Temperature and Solubility
Solid solubility and temperature
solubility increases with increasing temperature
solubility decreases with increasing temperature
Fractional crystallization is the separation of a mixture of substances into pure components on the basis of their differing solubilities.
Suppose you have 90 g KNO3 contaminated with 10 g NaCl.
Fractional crystallization:
1. Dissolve sample in 100 mL of water at 600C
2. Cool solution to 00C
3. All NaCl will stay in solution (s = 34.2g/100g)
4. 78 g of PURE KNO3 will precipitate (s = 12 g/100g). 90 g – 12 g = 78 g
Temperature and Solubility
Gas solubility and temperature
solubility usually decreases with
increasing temperature
Pressure and Solubility of Gases
The solubility of a gas in a liquid is proportional to the pressure of the gas over the solution (Henry’s law).
c = kP
c is the concentration (M) of the dissolved gas
P is the pressure of the gas over the solution
k is a constant (mol/L•atm) that depends onlyon temperature
low P
low c
high P
high c
Chemistry In Action: The Killer Lake
Lake Nyos, Cameroon, West Africa
Trigger?
• earthquake
• landslide
• strong Winds
1986 Aug. 21CO2 Cloud Released
1700 Casualties
Lake Nyos Degassing Schedule
Composition (1992) :• Layer 40 - 170 m :
– Water : 105 Mm3 – Gas: 190 Mm3
• Layer 170 - 208 m : – Water: 17.5 Mm3 – Gas: 80 Mm3 (1992)
5 pipes at 205 m, internal diameter = 139.8 mm;Liquid flow rate ˜ 2 Mm3/year/pipe
Conclusion: after 3 to 5 years, the situation will be safe.
Figure © Magma Production
총괄성
Colligative properties are properties that depend only on the number of solute particles in solution and not on the nature of the solute particles.
• number of solute particles
• [MA], mA, XA
• PB, mp, bp, .
Colligative Properties of Nonelectrolyte Solutions
Colligative properties are properties that depend only on the number of solute particles in solution and not on the nature of the solute particles.
Vapor-Pressure Lowering
Raoult’s law
If the solution contains only one solute:
X1 = 1 – X2
P 10 - P1 = P = X2 P 1
0 X2 = mole fraction of the solute
P 10 = vapor pressure of pure solvent
X1 = mole fraction of the solvent
P1 = X1 P 10
PA = XA P A0
PB = XB P B0
PT = PA + PB
Ideal Solution
PT = XA P A0 + XB P B
0
= XA P A0 + (1-XA )P B
0
=PB0 + XA (PA
0 – PB0)
Compisition at Vapor Phase
00
0
0
0
0
0
000
0
)1(
)1(
)(
/
A
B
A
A
AA
B
A
B
A
ABAB
AA
TAA
P
PM
XMM
X
XPP
PP
X
XPPP
PX
PPY
PT is greater thanpredicted by Raoults’s law
PT is less thanpredicted by Raoults’s law
ForceA-B
ForceA-A
ForceB-B< &
ForceA-B
ForceA-A
ForceB-B> &
Fractional Distillation Apparatus
Boiling-Point Elevation & Freezing-Point Depression
Tb = Tb – T b0
T b , T f is the boiling (freezing) point of the pure solvent
0
Tb , Tf is the boiling(freezing) point of the solution
Tb = Kb m
m is the molality of the solution
Kb , Kf is the molal boiling(freezing) -point elevation(depression) constant (0C/m)
Tf = T f – Tf0
0
Tf = Kf m
Gibbs Free Energy and Temperaturefor solid, liquid, vapor, solution
Gib
bs F
ree
Ene
rgy
solid
liquid
vapor
solution
TemperatureTfTf0 Tb
0 Tb
What is the freezing point of a solution containing 478 g of ethylene glycol (antifreeze) in 3202 g of water? The molar mass of ethylene glycol is 62.01 g. Kf water = 1.86 0C/m
Tf = Kf m
m =moles of solute
mass of solvent (kg)= 2.41 m=
3.202 kg solvent
478 g x 1 mol62.01 g
Tf = Kf m = 1.86 0C/m x 2.41 m = 4.48 0C
Tf = T f – Tf0
Tf = T f – Tf0 = 0.00 0C – 4.48 0C = -4.48 0C
Osmotic Pressure ()
Osmosis is the selective passage of solvent molecules through a porous membrane from a dilute solution to a more concentrated one.
A semipermeable membrane allows the passage of solvent molecules but blocks the passage of solute molecules.
Osmotic pressure () is the pressure required to stop osmosis.
dilutemore
concentrated
HighP
LowP
Osmotic Pressure ()
= MRT
M is the molarity of the solution
R is the gas constant
T is the temperature (in K)
A cell in an:
isotonicsolution
hypotonicsolution
hypertonicsolution
Colligative Properties of Nonelectrolyte Solutions
Colligative properties are properties that depend only on the number of solute particles in solution and not on the nature of the solute particles.
Vapor-Pressure Lowering P1 = X1 P 10
Boiling-Point Elevation Tb = Kb m
Freezing-Point Depression Tf = Kf m
Osmotic Pressure () = MRT
Colligative Properties of Electrolyte Solutions
0.1 m NaCl solution 0.1 m Na+ ions & 0.1 m Cl- ions
Colligative properties are properties that depend only on the number of solute particles in solution and not on the nature of the solute particles.
0.1 m NaCl solution 0.2 m ions in solution
van’t Hoff factor (i) = actual number of particles in soln after dissociation
number of formula units initially dissolved in soln
nonelectrolytesNaCl
CaCl2
i should be
12
3
Boiling-Point Elevation Tb = i Kb m
Freezing-Point Depression Tf = i Kf m
Osmotic Pressure () = iMRT
Colligative Properties of Electrolyte Solutions
A colloid is a dispersion of particles of one substance throughout a dispersing medium of another substance.
Colloid versus solution
• collodial particles are much larger than solute molecules
• collodial suspension is not as homogeneous as a solution
The Cleansing Action of Soap
C15H31 사슬
COO- 기
The Cleansing Action of Soap
Grease Hydrophilic Head
Hydrophobic Tail
Chemistry In Action: Desalination
>26 bar
13 장 용액의 물리적 성질 - 요약
• 구성과 구성비 ( 농도 )• 용해와 용해도• 총괄성
용액의 물리적 성질 - 균일 혼합물의 구성
• 용액 - 균일 혼합물• 구성물 – 용매 , 용질• 구성비 – 농도 - 물리적 표현 , 화학적 표현• 농도 단위 - 몰 [M], 몰랄 (m), 몰분율 (X)• 구성 한계 - 용해도
용액의 물리적 성질 - 용해
• 용해와 용해도 - 포화 , 불포화 , 과포화• 용해과정의 분자적 고찰 - 용질 , 용매 분자간
상호작용• 용해도에 미치는 온도의 영향 - 재결정
• 기체의 용해도에 미치는 압력의 영향 – Henry’s Law
• 용해도에 미치는 온도의 영향• 액체의 경우 - 재결정• 기체의 경우
용액의 물리적 성질 - 총괄성
• 총괄성 – Raoult’s Law, van’t Hoff factor• 분압 ,• 끓는점• 녹는점• 삼투압
• 분별증류• 분자량측정• 역삼투