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Copyright 2004 - John Sayles 1

AP Review Unit 2

Solutions

and

Solution Equilibrium


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”


The Dissolving of Lithium Fluoride in Water

Copyright © Houghton Mifflin Company. All rights reserved 12-8

12_8


Solvation of Ions

12-7 Copyright © Houghton Mifflin Company. All rights reserved


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


Comparison of Unsaturated and Saturated Solutions



Effect of Pressures on Gas Solubility



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


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


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


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



Semipermeable

Membrane


Demonstration of Vapor-Pressure Lowering



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


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


Solubility Product Constants, Ksp, at 25º C

Table 17-B Copyright © Houghton Mifflin Company. All rights reserved

T17_1B

Mg3(AsO4)2

MgCO3

Mg(OH)2

MgC2O4

MnS

Hg2Cl2HgS

Ni(OH)2

NiS

AgC2H3O2

AgBr

AgCl

AgCrO4

AgI

Ag2S

SrCO3

SrCrO4

SrSO4

Zn(OH)2

ZnS

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

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

Formula KspSubstance

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