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Chap13 - Solutions and Chap13 - Solutions and Colligative PropertiesColligative Properties
A solution is a solute (A) dissolved A solution is a solute (A) dissolved into a solvent (B).into a solvent (B).
Solvent B
Solute A
A. ConcentrationA. Concentration
1. Mass Percent1. Mass Percent
= = mass component mass component x 100 x 100 total mass solution total mass solution
= = grams A grams A x 100 x 100
grams A + grams Bgrams A + grams B
2. Parts per million (ppm)2. Parts per million (ppm)
= = mass componentmass component x 10x 1066
total mass solutiontotal mass solution
ppt = x 10ppt = x 1033 ( ) ( )
ppb = x 10ppb = x 109 9 ( )( )
Parts per thousand
Parts per billion
3. Mole fraction (X)3. Mole fraction (X)
= = mole componentmole component
total molestotal moles
XXAA = mole A = mole A
mole A + mole Bmole A + mole B
4. Molarity (M)4. Molarity (M)
= = moles of solutemoles of solute
Liters of solutionLiters of solution
M = mole AM = mole A
L solutionL solution
3.16 g MgBr2 1 mol = 0.0172 mol MgBr2
184.1 g MgBr2
*Remember*1L = 1000mL
0.859 L
Look at Problem #1
= 0.0200 M
5. Molality (m)5. Molality (m)
= = moles solutemoles solute
kg solventkg solvent
m = m = mole Amole A
kg Bkg B *Remember*1g = 1mL for H2O 1000g = 1 kg
4.8 g NaCL 1 mol = 0.0821 mol NaCl
58.5 g NaCl 0.5 kg
Look at Problem #4
= 0.164 m
Dilution of SolutionDilution of Solution
MM11VV1 1 = M= M22VV22
Answer to Worksheet
3a – 50 mL diluted3b – 1.28 mL diluted
Conversion between UnitsConversion between Units
For HFor H22O only, Molarity = molality.O only, Molarity = molality.
Why? Because the density of HWhy? Because the density of H22O is equal O is equal
to 1.00 g/mL.to 1.00 g/mL.
Therefore, 1000mL = 1000gTherefore, 1000mL = 1000g 1 L = 1 kg1 L = 1 kg
Conversion between UnitsConversion between Units
For any other solution other than an For any other solution other than an aqueous solution - aqueous solution - YOU MUST YOU MUST
USE THE USE THE DENSITYDENSITY!!!!!!!!!!
Use the density to convert mass to Use the density to convert mass to volume.volume.
Conversion between UnitsConversion between Units
mass solvent
mass solute
mass solution
volume solution
moles solutemolarmass
M = mole/L
m = mole/kg
density
+ add
Conversion between UnitsConversion between Units
mass solvent
mass solute
mass solution
volume solution
moles solutemolarmass
M = mole/L
m = mole/kg
density
+ add
1000 g = 1 kg
1000 mL = 1 L
Conversion between UnitsConversion between Units
molarmass
density
+ add
1000 g = 1 kg
1000 mL = 1 L
Your homework/classwork is Your homework/classwork is worksheet –worksheet –
concentration conversionsconcentration conversions
Convert mass % to …..Convert mass % to …..
5% HC5% HC22HH33OO22 5 g x 1mol/60g = 5 g x 1mol/60g =
0.0833 mol0.0833 mol
95% H95% H22O O 95 g x 1mol/18g = 95 g x 1mol/18g =
5.28 mol5.28 mol
Mole fractionMole fraction
X = X = 0.0833mol0.0833mol / ( / (0.0833 mol0.0833 mol + + 5.28 mol5.28 mol))
m = m = 0.0833 mol0.0833 mol / / 0.095 kg0.095 kg
molalitymolality
convert 95 g
Convert M to mConvert M to m
1.13 1.13 mol mol to to mol mol L L solutionsolution kg kg solventsolvent
1000 mL x 1.05 g/ml = 1050 g solution1000 mL x 1.05 g/ml = 1050 g solution
1.13 mole KOH x 56.1 g/mol = 63.4 g solute1.13 mole KOH x 56.1 g/mol = 63.4 g solute
density
1050 g solution 1050 g solution
– – 63.4 g KOH63.4 g KOH
986.6 g solvent986.6 g solvent
m = m = 1.13 mol KOH 1.13 mol KOH = 1.15= 1.15 mol mol
0.9866 kg kg0.9866 kg kg
What about mass percent?What about mass percent?
1050 g solution
63.4 g KOH
100*solution g
solute g % Mass
100*solution g 1050
KOH g 63.4 % Mass
Dimensional AnalysisDimensional Analysis
What is the molarity of concentrated HCl?What is the molarity of concentrated HCl? 39.0% HCl by mass and 1.13 g/mL density39.0% HCl by mass and 1.13 g/mL density
ML
mL
mL
g
g
Mole
sog
HClg1.12
1
1000*
1
13.1*
5.36
1*
ln100
0.39
Solution CalculationsSolution Calculations
What is the molarity What is the molarity of a 1.11 ppm solution of a 1.11 ppm solution of Znof Zn2+2+ ions? ions?
MXg
Znmole
mg
g
liter
Znmg 52
1070.139.65
1*
1000
1*
1
11.1
Solid CalculationsSolid Calculations
Chemical analysis showed 1.23 mg Fe in a Chemical analysis showed 1.23 mg Fe in a
15.67 g sample of soil.15.67 g sample of soil. What is the Fe concentration in ppm?What is the Fe concentration in ppm?
ppmmg
g
sampleg
Femg5.7810*
1000
1*
67.15
23.1 6
Unusual concentration unitsUnusual concentration units
How many nano moles of Cu are present in 12.3 How many nano moles of Cu are present in 12.3 µL of 25 ppm CuSOµL of 25 ppm CuSO44??
molenmolem
molen
mg
molem
L
mg
L
LL 93.1
1
10*
65.159
1*
25*
10
1*3.12
6
6
B. Colligative PropertiesB. Colligative Properties
1. Boiling Point Elevation1. Boiling Point Elevation
ΔTΔTbb = k = kb b • m • • m • ii
for an aqueous solutionfor an aqueous solution
TTbb = 100 = 100ooCC + (0.52 + (0.52 ooC/m) •(m)C/m) •(m)
* note that as molality increases * note that as molality increases
ΔTΔTb b increases as wellincreases as well
Normal B.P. Kbfor water
B. Colligative PropertiesB. Colligative Properties
2. Freezing Point Depression2. Freezing Point Depression
ΔTΔTff = k = kf f • m • • m • ii
for an aqueous solutionfor an aqueous solution
TTff = 0 = 0ooCC - (1.86 - (1.86 ooC/m) •(m)C/m) •(m)
* note that as molality increases * note that as molality increases
ΔTΔTf f increases as wellincreases as well
Normal F.P. Kf for water
Ex. Non-electrolyte (Ex. Non-electrolyte (ii=1)=1)
Antifreeze is made at 25% CAntifreeze is made at 25% C22HH66OO22 by mass. by mass.
What is the T What is the Tb b and the Tand the Tff??
Make your life easy and assume 1000g.Make your life easy and assume 1000g. Why? Because molality is based upon kg of Why? Because molality is based upon kg of
solventsolvent Mass percentMass percent 250 g C 250 g C22HH66OO22
750 g H750 g H22OO
Boiling and Freezing PointBoiling and Freezing Point
mkg
mole
g
molegm 37.5
750.0
03.4
1.62
1250
CmmCCTb 8.102)37.5()/52.0(100
molalitymolality
CmmCCTf 10)37.5()/86.1(0
C2H6O2 H2O
Ex. Molecular Weight of UnknownEx. Molecular Weight of Unknown
What is the MM of a sample if 250grams of What is the MM of a sample if 250grams of the sample is placed into 1000grams of the sample is placed into 1000grams of water and the temperature rose by 3.5water and the temperature rose by 3.5°C?°C?
)(?)/52.0(1005.103 mmCCC
mkg
mole?73.6
Assuming 1000g (1kg), the molality Assuming 1000g (1kg), the molality becomes…..becomes…..
molekgkg
mole73.6173.6
moleMM
g73.6
?
250
molegMM /37
Ex. Electrolyte (Ex. Electrolyte (ii = ?) = ?) IMPORTANT – the colligative properties IMPORTANT – the colligative properties
of freezing point and boiling point are of freezing point and boiling point are proportional to the number of particles proportional to the number of particles present in the solution.present in the solution.
van Hoft factor, van Hoft factor, ii NaCl NaCl ii = 2 moles = 2 moles Ie. 1m = 2m Ie. 1m = 2m CaClCaCl22 i = i = 3 moles3 moles Ie. 1m = 3m Ie. 1m = 3m
AlAl22(SO(SO44))33 i = i = 5 moles5 moles Ie. 1m = 5m Ie. 1m = 5mincreasingcolligative
effect
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