Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Ch 4: Types of Rxns and Solution Stoik Read for comprehension pp

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 2 Aqueous Solutions Water is the dissolving medium, or solvent.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 3 Some Properties of Water 4 Water is “bent” or V-shaped. 4 The O-H bonds are covalent. 4 Water is a polar molecule. 4 Hydration occurs when salts dissolve in water.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 4 Figure 4.1 The Water Molecule is Polar

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 5 Solute/Solvent Solute: -- dissolves in water (or other “solvent”) --is present in lesser amount (if the same phase as the solvent) Solvent: --is present in greater amount (if the same phase as the solute)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 6 Like Dissolves Like Rule of thumb: polar solvents dissolve polar/ionic solutes nonpolar solvents dissolve nonpolar solutes

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 7 Figure 4.2 Polar Water Molecules Interact with the Positive and Negative Ions of a Salt

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 8 Figure 4.3 Polar Bond in ethanol

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 9 Figure 4.5 BaCl 2 Dissolving Dissociation: BaCl 2 (s) --> Ba 2+ (aq) + 2Cl - (aq)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 10 Electrolytes Strong - conduct current efficiently Salts: NaCl Strong acids: HNO 3 Strong bases Weak - conduct only a small current Weak acids/bases:acetic acid/ammonia Tap water Non - no current flows pure water, sugar solution

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 11 Acids Strong acids -dissociate completely to produce H + in solution hydrochloric and sulfuric acid Weak acids - dissociate to a slight extent to give H + in solution acetic and formic acid

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 12 Figure 4.6 HCI (aq) is Completely Ionized

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 13 Figure 4.8 Acetic Acid in Water

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 14 Bases Strong bases - react completely with water to give OH  ions. sodium hydroxide Weak bases - react only slightly with water to give OH  ions. ammonia

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 15 Figure 4.7 An Aqueous Solution of Sodium Hydroxide

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 16 Figure 4.9 The Reaction of NH 3 in Water

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 17 Molarity Molarity (M) = moles of solute per volume of solution in liters:

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 18 Common Terms of Solution Concentration Stock - routinely used solutions prepared in concentrated form. Concentrated - relatively large ratio of solute to solvent. (5.0 M NaCl) Dilute - relatively small ratio of solute to solvent. (0.01 M NaCl)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 19 Figure 4.10 Preparation of a Standard Solution

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 20 Figure 4.11 (a) A Measuring Pipet(b) A Volumetric (transfer) Pipet

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 21 Types of Solution Reactions 4 Precipitation reactions AgNO 3 (aq) + NaCl(aq)  AgCl(s) + NaNO 3 (aq) 4 Acid-base reactions NaOH(aq) + HCl(aq)  NaCl(aq) + H 2 O(l) 4 Oxidation-reduction reactions Fe 2 O 3 (s) + Al(s)  Fe(l) + Al 2 O 3 (s)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 22 Simple Rules for Solubility 1.Most nitrate (NO 3  ) salts are soluble. 2.Most alkali (group 1A) salts and NH 4 + are soluble. 3.Most Cl , Br , and I  salts are soluble (NOT Ag +, Pb 2+, Hg 2 2+ ) 4.Most sulfate salts are soluble (NOT BaSO 4, PbSO 4, HgSO 4, CaSO 4 ) 5.Most OH  salts are only slightly soluble (NaOH, KOH are soluble, Ba(OH) 2, Ca(OH) 2 are marginally soluble) 6.Most S 2 , CO 3 2 , CrO 4 2 , PO 4 3  salts are only slightly soluble.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 23 Figure 4.14 The Reaction of K 2 CrO 4 (aq) and Ba(NO 3 ) 2 (aq)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 24 Describing Reactions in Solution 1.Molecular equation (reactants and products as compounds) AgNO 3 (aq) + NaCl(aq)  AgCl(s) + NaNO 3 (aq) 2.Complete ionic equation (all strong electrolytes shown as ions) Ag + (aq) + NO 3  (aq) + Na + (aq) + Cl  (aq)  AgCl(s) + Na + (aq) + NO 3  (aq)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 25 Describing Reactions in Solution (continued) 3.Net ionic equation (show only components that actually react) Ag + (aq) + Cl  (aq)  AgCl(s) Na + and NO 3  are spectator ions.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 26 Figure 4.16 The Reaction of KCI(aq) and AgNO 3 (aq)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 27 Performing Calculations for Acid-Base Reactions 1.List initial species and predict reaction. 2.Write balanced net ionic reaction. 3.Calculate moles of reactants. 4.Determine limiting reactant. 5.Calculate moles of required reactant/product. 6.Convert to grams or volume, as required.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 28 Key Titration Terms Titrant - solution of known concentration used in titration Analyte - substance being analyzed Equivalence point - enough titrant added to react exactly with the analyte Endpoint - the indicator changes color so you can tell the equivalence point has been reached.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 29 Rules for Assigning Oxidation States 1. Oxidation state of an atom in an element = 0 2. Oxidation state of monatomic element = charge 3. Oxygen =  2 in covalent compounds (except in peroxides where it =  1) 4. H = +1 in covalent compounds 5. Fluorine =  1 in compounds 6. Sum of oxidation states = 0 in compounds Sum of oxidation states = charge of the ion

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 30 Balancing by Half-Reaction Method 1.Write separate reduction, oxidation reactions. 2.For each half-reaction:  Balance elements (except H, O)  Balance O using H 2 O  Balance H using H +  Balance charge using electrons

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 31 Balancing by Half-Reaction Method (continued) 3.If necessary, multiply by integer to equalize electron count. 4.Add half-reactions. 5.Check that elements and charges are balanced.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 32 Half-Reaction Method - Balancing in Base 1.Balance as in acid. 2.Add OH  that equals H + ions (both sides!) 3.Form water by combining H +, OH . 4.Check elements and charges for balance.