AP Review Unit 2. Solutions and Solution Equilibrium. Copyright John Sayles 1

Transcription

1 AP Review Unit 2 Solutions and Solution Equilibrium Copyright John Sayles 1

2 The Solution Process Break solute-solute bonds IMF s if covalent Ionic bonds if ionic Break solvent-solvent bonds Likely IMF s Form solute-solvent bonds END END EX The payoff; if this goes well, sol n forms Known as solvation (or hydration) The reason like dissolves like Copyright John Sayles 2

3 The Dissolving of Lithium Fluoride in Water 12_8 Copyright Houghton Mifflin Company. All rights reserved 12-8 Copyright John Sayles 3

4 Solvation of Ions Copyright Houghton Mifflin Company. All rights reserved Copyright John Sayles

5 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 PP x Temp, surface area and stirring affect rate Copyright John Sayles 5

6 Comparison of Unsaturated and Saturated Solutions Copyright Houghton Mifflin Company. All rights reserved 12-3 Copyright John Sayles 6

7 Effect of Pressures on Gas Solubility Copyright Houghton Mifflin Company. All rights reserved Copyright John Sayles 7

8 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 John Sayles 8

9 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 A x B y, van t Hoff factor = x + y Radicals do not split into pieces; they re covalently bonded Copyright John Sayles 9

10 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 John Sayles 10

11 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 John Sayles 11

12 Semipermeable Membrane Copyright Houghton Mifflin Company. All rights reserved Copyright John Sayles 12

13 Demonstration of Vapor-Pressure Lowering Copyright Houghton Mifflin Company. All rights reserved Copyright John Sayles 13

14 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 k f and k b depend on solvent; found in tables Calculate m from formula Calculate moles from m Do #67 on page 545 Copyright John Sayles 14

15 Solution Equilbrium K sp = [cation] x [anion] y for C x A y Just like any other K; used in same ways Estimate solubility Calculate one [ ] given the other [ ] Predicting PPT Calculate Q and compare to K sp Solubility <---> K sp If solubility = x, K sp = x 2, 4x 3,, 108x 5 If common ion is present Make grid Make one [ ] initial 0 Copyright John Sayles 15

16 Solubility Product Constants, Ksp, at 25º C T17_1B Substance Formula K sp 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 Mg 3 (AsO 4 ) 2 MgCO 3 Mg(OH) 2 MgC 2 O 4 MnS Hg 2 Cl 2 HgS Ni(OH) 2 NiS AgC 2 H 3 O 2 AgBr AgCl AgCrO 4 AgI Ag 2 S SrCO 3 SrCrO 4 SrSO 4 Zn(OH) 2 ZnS 2 x x x x x x x x x x x x x x x x x x x x Copyright Houghton Mifflin Company. All rights reserved Copyright John Sayles 16 Table 17-B