AP Review Unit 2
Solutions
and
Solution Equilibrium
Copyright 2004 - John Sayles
1
The “Solution Process”
Break solute-solute bonds
END
IMF’s if covalent
Ionic bonds if ionic
Break solvent-solvent bonds
END
Likely IMF’s
Form solute-solvent bonds
EX
The payoff; if this goes well, sol’n forms
Known as solvation (or hydration)
The reason “like dissolves like”
Copyright 2004 - John Sayles
2
The Dissolving of Lithium Fluoride in Water
12_8
Copyright
©
12-8
Houghton Mifflin Company. All rights reserved
Copyright 2004 - John Sayles
3
Solvation of Ions
Copyright
©
12-7
Houghton Mifflin Company. All rights reserved
Copyright 2004 - John Sayles
4
Solubility
Def’n: max. [ ], [ ] at equilibrium, [ ]
of a saturated solution
Depends on
Nature (polarity) of solute and solvent
Temp (endo or exo?)
Pressure, for gases [ ]x prop to PPx
Temp, surface area and stirring affect rate
Copyright 2004 - John Sayles
5
Comparison of Unsaturated and Saturated Solutions
Copyright
©
12-3
Houghton Mifflin Company. All rights reserved
Copyright 2004 - John Sayles
6
Effect of Pressures on Gas Solubility
Copyright
©
12-12
Houghton Mifflin Company. All rights reserved
Copyright 2004 - John Sayles
7
Solubility Rules
See page 136
Solubles
Anions: nitrates, acetates, halides, sulfates
(except Ca, Sr, Ba)
Cations; Group I, ammonium
Insolubles
Anions: sulfides, hydroxides, carbonates,
phosphates
Cations: Ag, Pb, Hg
Copyright 2004 - John Sayles
8
Van t’Hoff Factor
Covalent solute crystal split into molecules
Van t’Hoff factor = i = 1
Covalent solutes are non-electrolytes
Ionic solute crystal splits into ions
For AxBy, van t’Hoff factor = x + y
Radicals do not split into pieces; they’re
covalently bonded
Copyright 2004 - John Sayles
9
Units of Concentration
Molarity = M = moles solute/liter solution
molality = m = moles solute/kg solvent
Custom-made for BP elev and MP depression
Mole fraction = X = moles solute/moles total
Used in Dalton’s (PP’s) and Raoult’s laws (VP lowering)
Percent = % = mass solute/mass total
To convert between units
Pick sample = denominator of given unit
Use density of solution to change grams <--> liters
Do #55 on page 544
Copyright 2004 - John Sayles
10
Colligative Properties
Ways in which a solution differs from the
pure solvent
Find these on the formula sheet
VP is lower (Raoult’s Law)
BP is higher, since the VP is lower
MP is lower; the liquid range is extended twice
Osmotic pressure created in presence of SPM
Copyright 2004 - John Sayles
11
Semipermeable
Membrane
Copyright
©
12-21
Houghton Mifflin Company. All rights reserved
Copyright 2004 - John Sayles
12
Demonstration of Vapor-Pressure Lowering
Copyright
©
12-15
Houghton Mifflin Company. All rights reserved
Copyright 2004 - John Sayles
13
Using Colligative Properties
Great way to count moles for a non-gas!
Make sol’n and compare BP (or other prop) to
that of pure solvent
Use formula to calculate moles, then MW
kf and kb depend on solvent; found in tables
Calculate m from formula
Calculate moles from m
Do #67 on page 545
Copyright 2004 - John Sayles
14
Solution Equilbrium
Ksp = [cation]x[anion]y for CxAy
Just like any other K; used in same ways
Estimate solubility
Calculate one [ ] given the other [ ]
Predicting PPT
Calculate Q and compare to Ksp
Solubility <---> Ksp
If solubility = x, Ksp= x2, 4x3, … , 108x5
If common ion is present
Make grid
Make one [ ]initial ≠ 0
Copyright 2004 - John Sayles
15
Solubility Product Constants, Ksp, at 25º C
T 17_1B
Copyright
©
Substance
Formula
Ksp
Magnesium arsenate
Magnesium carbonate
Magnesium hydroxide
Magnesium oxalate
Manganese(II) sulfide
Mercury(I) chloride
Mercury(II) sulfide
Nickel(II) hydroxide
Nickel(II) sulfide
Silver acetate
Silver bromide
Silver chloride
Silver chromate
Silver iodide
Silver sulfide
Strontium carbonate
Strontium chromate
Strontium sulfate
Zinc hydroxide
Zinc sulfide
Mg3(AsO 4)2
MgCO3
Mg(OH)2
MgC2O4
MnS
Hg2Cl2
HgS
Ni(OH)2
NiS
AgC 2H3O2
AgBr
AgCl
AgCrO 4
AgI
Ag 2S
SrCO3
SrCrO4
SrSO4
Zn(OH)2
ZnS
2 x 10 -20
1.0 x 10 -5
1.8 x 10 -11
8.5 x 10 -5
2.5 x 10 -10
1.3 x 10 -18
1.6 x 10 -52
2.0 x 10 -15
3 x 10 -19
2.0 x 10 -3
5.0 x 10 -13
1.8 x 10 -10
1.1 x 10 -12
8.3 x 10 -17
6 x 10 -50
9.3 x 10 -10
3.5 x 10 -5
2.5 x 10 -7
2.1 x 10 -16
1.1 x 10 -21
Table 17-B
Houghton Mifflin Company. All rights reserved
Copyright 2004 - John Sayles
16