Reactions in Aqueous Solution Student Version

Chapter 4Reactions in Aqueous SolutionCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Describing Chemical ReactionsA chemical reaction is the process by which one or more substances are changed into one or more different substances

(NH4)2Cr2O7(s) N2(g) + Cr2O3(s) + 4H2O(g)The reactant ammonium dichromate yields the products nitrogen, chromium (III) oxide and water

A CHEMICAL EQUATION represents, with symbols and formulas, the identifies and relative amounts of the reactants and products in a chemical equationreactantsproducts*

Indications of a Chemical ReactionEvolution of heat and light is strong evidence that a chemical reaction has taken place! But, the evolution of heat or light by itself is not necessarily a sign of a chemical change since many physical changes also release either heat or light. Production of gas! (aka bubbles when two substances are mixed)Formation of precipitate! A solid that is produced as a result of a chemical reaction in solution and that separates from the solution is known as a precipitateColor Change!*

Characteristics of Chemical EquationsThe equation must represent all reactants and products.The equation must contain the correct formulas for the reactants and productsThe law of conservation of mass MUST be satisfied!!

Law of conservation of mass atoms are neither created nor destroyed in ordinary chemical reactions

To equalized numbers of atoms, coefficients are added in front of the formulas where necessary*

Types of Chemical ReactionsA + B CC A + BA + BC AC + BAB + CD AD + CB

Acid + Base salt + waterChange of oxidation stateHydrocarbon + O2 CO2 + H2O*Synthesis (Combination)DecompositionSingle ReplacementPrecipitation Reactions (Double Replacement Reactions)Neutralization Reactions (Acid/Base)Redox ReactionsCombustion

PRECIPITATION REACTIONSDouble Replacement ReactionsAB + CD AD + BC*

*A solution is a homogenous mixture of 2 or more substancesThe solute is(are) the substance(s) present in the smaller amount(s)The solvent is the substance present in the larger amountSoft drink (l)Air (g)Soft Solder (s)H2ON2PbSugar, CO2O2, Ar, CH4Sn

*An electrolyte is a substance that, when dissolved in water, results in a solution that can conduct electricity.A nonelectrolyte is a substance that, when dissolved, results in a solution that does not conduct electricity.

*Strong Electrolyte 100% dissociationWeak Electrolyte not completely dissociatedConduct electricity in solution?Cations (+) and Anions (-)

*Ionization of acetic acidCH3COOH CH3COO- (aq) + H+ (aq)A reversible reaction. The reaction can occur in both directions.Acetic acid is a weak electrolyte because its ionization in water is incomplete.

*Hydration is the process in which an ion is surrounded by water molecules arranged in a specific manner.

*Nonelectrolyte does not conduct electricity?No cations (+) and anions (-) in solution

Precipitation Reactions*Precipitate insoluble solid that separates from solutionmolecular equationionic equationnet ionic equationK+ and NO3- are spectator ions

Precipitation of Lead Iodide*PbI2

*Solubility is the maximum amount of solute that will dissolve in a given quantity of solvent at a specific temperature.

*Examples of Insoluble CompoundsCdSPbSNi(OH)2Al(OH)3

Problem 4.20*Characterize the following compounds as soluble or (b) insoluble in water:CaCO3ZnSO4Hg(NO3)2HgSO4NH4ClO4

Writing Net Ionic Equations*Write the balanced molecular equation.Write the ionic equation showing the strong electrolytes completely dissociated into cations and anions.Cancel the spectator ions on both sides of the ionic equationCheck that charges and number of atoms are balanced in the net ionic equationWrite the net ionic equation for the reaction of silver nitrate with sodium chloride.

*Predict what happens when a potassium hydroxide solution is mixed with a solution of sodium chloride. Write a net ionic equation for the reaction.

*What do we expect to see if we add copper (II) sulfate to sodium hydroxide? Write the molecular equation, ionic equation, and net ionic equation.

*Predict what happens when a potassium phosphate solution is mixed with a solution of calcium nitrate. Write a net ionic equation for the reaction.EXTRA PRACTICE

*Predict what happens when a silver nitrate solution is mixed with a solution of potassium hydroxide. Write a net ionic equation for the reaction.

Types of Chemical ReactionsA + B CC A + BA + BC AC + BAB + CD AD + BC


NEUTRALIZATION REACTIONSAcid/Base ReactionsAcid + Base Salt + Water*

Properties of Acids*Have a sour taste. Vinegar owes its taste to acetic acid. Citrusfruits contain citric acid.React with certain metals to produce hydrogen gas.React with carbonates and bicarbonatesto produce carbon dioxide gasCause color changes in plant dyes.Aqueous acid solutions conduct electricity.

*Have a bitter taste.Feel slippery. Many soaps contain bases.Properties of BasesCause color changes in plant dyes.Aqueous base solutions conduct electricity.Examples:

*Arrhenius acid is a substance that produces H+ (H3O+) in waterArrhenius base is a substance that produces OH- in water

*Hydronium ion, hydrated proton, H3O+

*A Brnsted acid is a proton donorA Brnsted base is a proton acceptoracidbaseacidbaseA Brnsted acid must contain at least one ionizable proton!

*Monoprotic acidsStrong electrolyte, strong acidStrong electrolyte, strong acidWeak electrolyte, weak acidDiprotic acidsStrong electrolyte, strong acidWeak electrolyte, weak acidTriprotic acidsWeak electrolyte, weak acidWeak electrolyte, weak acidWeak electrolyte, weak acid

*Identify each of the following species as a Brnsted acid, base, or both. (a) HI, (b) CH3COO-, (c) H2PO4-Brnsted acidBrnsted baseBrnsted acidBrnsted base

Problem 4.32*Identify each of the following as either aBrnsted acid, (b) Brnsted base, or (c) both.PO43-ClO2-NH4+HCO3-

Neutralization Reaction*

Neutralization Reaction Involving a Weak Electrolyte*

Neutralization Reaction Producing a Gas*

Types of Chemical ReactionsA + B CC A + BA + BC AC + BAB + CD AD + BC


OXIDATION REDUCTION REACTIONSRedox ReactionsSynthesis Reactions:A + B CDecomposition Reactions:C A + BSingle Replacement Reactions: A + BC AC + B Combustion Reactions:hydrocarbon + O2 CO2 + H2O *

Oxidation-Reduction Reactions*(electron transfer reactions)Oxidation half-reaction (lose e-)Reduction half-reaction (gain e-)

*Zn is oxidizedCu2+ is reducedZn is the reducing agentCu2+ is the oxidizing agentCopper wire reacts with silver nitrate to form silver metal.What is the oxidizing agent in the reaction?

Oxidation number*The charge the atom would have in a molecule (or anionic compound) if electrons were completely transferred.Free elements (uncombined state) have an oxidation number of zero.Na, Be, K, Pb, H2, O2, P4 = 0In monatomic ions, the oxidation number is equal to the charge on the ion.Li+, Li = +1; Fe3+, Fe = +3; O2-, O = -2The oxidation number of oxygen is usually 2. In H2O2 and O22- it is 1. 4.4

*The oxidation number of hydrogen is +1 except when it is bonded to metals in binary compounds. In these cases, its oxidation number is 1.6. The sum of the oxidation numbers of all the atoms in a molecule or ion is equal to the charge on the molecule or ion.Group IA metals are +1, IIA metals are +2 and fluorine is always 1.HCO3-O = 2H = +13x(2) + 1 + ? = 1C = +4What are the oxidation numbers of all the elements in HCO3- ?7. Oxidation numbers do not have to be integers. Oxidation number of oxygen in the superoxide ion, O2-, is .

*The Oxidation Numbers of Elements in their Compounds

*NaIO3Na = +1O = -23x(-2) + 1 + ? = 0I = +5IF7F = -17x(-1) + ? = 0I = +7K2Cr2O7O = -2K = +17x(-2) + 2x(+1) + 2x(?) = 0Cr = +6What are the oxidation numbers of all the elements in each of these compounds? NaIO3 IF7 K2Cr2O7

Problem 4.50*Give the oxidation number for the underlined atoms or in each of the following species:Mg3N2b) CsO2c) CaC2CO32-e) C2O42-f) ZnO22-g) NaBH4h) WO42-

Types of Oxidation-Reduction Reactions*Synthesis/Combination ReactionDecomposition Reaction00+3-1+1+5-2+1-10

Types of Oxidation-Reduction Reactions*Combustion Reaction00+4-200+2-2

Types of Oxidation-Reduction Reactions*Displacement ReactionHydrogen DisplacementMetal DisplacementHalogen Displacement0+1+200+40+20-1-10

*The Activity Series for MetalsHydrogen Displacement ReactionM is metalBC is acid or H2OB is H2

Problem 4.52*Which of the following metals can react with water to produce H2 (g)?AuLiHgCaPt

*The Activity Series for HalogensHalogen Displacement Reaction0-1-10F2 > Cl2 > Br2 > I2

Types of Oxidation-Reduction Reactions*The same element is simultaneously oxidized and reduced.

Example:Disproportionation Reaction0+1-1oxidizedreduced

*Classify each of the following reactions.

Problem 4.54*Predict the outcome of the reactions represented by the following equations by using the activity series, and balance the equations.

Cu (s) + HCl (aq) I2 (g) + NaBr (aq) Mg (s) + CuSO4 (aq) Cl2 (g) + KBr (aq)

Problem 4.56*Classify the following redox reactions by type:

P4 + 10Cl2 4PCl52NO N2 + O2Cl2 + 2KI I2 + 2KCl

Solution StoichiometryMolarityDilutionsGravimetric AnalysisTitrations*

*Solution StoichiometryThe concentration of a solution is the amount of solute present in a given quantity of solvent or solution.What mass of KI is required to make 5.00 x 102 mL of a 2.80 M KI solution?M KIM KI5.00x102 mL= 232 g KI

Problem 4.60*Calculate the mass in grams of sodium nitrate required to prepare 2.50 x 102 mL of a 0.707 M solution.

*Preparing a Solution of Known Concentration

*Dilution is the procedure for preparing a less concentrated solution from a more concentrated solution.

*How would you prepare 60.0 mL of 0.200 M HNO3 from a stock solution of 4.00 M HNO3?MiVi = MfVfMi = 4.00 MMf = 0.200 MVf = 0.0600 LVi = ? L = 0.00300 L = 3.00 mLDilute 3.00 mL of acid with water to a total volume of 60.0 mL.

Problem 4.70*Water is added to 25.0 mL of a 0.866 M KNO3 solution until the volume of the solution is exactly 500 mL. What is the concentration of the final solution?

Problem 4.72*You have 505 mL of a 0.125 M HCl solution and you want to dilute it to exactly 0.100 M. How much water should you add? (assume that the volumes are additive.)

*Gravimetric AnalysisDissolve unknown substance in waterReact unknown with known substance to form a precipitateFilter and dry precipitateWeigh precipitateUse chemical formula and mass of precipitate to determine amount of unknown ion

*A 0.5662 g sample of an ionic compound containing chloride ions and an unknown metal is dissolved in water, and treated with excess AgNO3. If 1.0882 g of AgCl precipitate forms, what is the percent by mass of Cl in the original compound?

Problem 4.78*A sample of 0.6760 g of an unknown compound containing barium ions (Ba2+) is dissolved in water and treated with an excess of Na2SO4. If the mass of the BaSO4 precipitate formed is 0.4105 g, what is the percent by mass of Ba in the original unknown compound?

*TitrationsIn a titration a solution of accurately known concentration is added gradually added to another solution of unknown concentration until the chemical reaction between the two solutions is complete.Equivalence point the point at which the reaction is completeIndicator substance that changes color at (or near) the equivalence point Slowly add baseto unknown acidUNTILthe indicatorchanges color

*Titrations can be used in the analysis of Acid-base reactions

Redox reactions

*What volume of a 1.420 M NaOH solution is required to titrate 25.00 mL of a 4.50 M H2SO4 solution?WRITE THE CHEMICAL EQUATION!25.00 mL= 158 mL

Problem 4.86*Calculate the concentration (in molarity) of a NaOH solution if 25.0 mL of the solution are needed to neutralize 17.4 mL of a 0.312 M HCl solution.

*WRITE THE CHEMICAL EQUATION!0.01642 L= 0.4358 M16.42 mL of 0.1327 M KMnO4 solution is needed to oxidize 25.00 mL of an acidic FeSO4 solution. What is the molarity of the iron solution?16.42 mL = 0.01642 L25.00 mL = 0.02500 L

Problem 4.92*The SO2 present in air is mainly responsible for the acid rain phenomenon. Its concentration can be determined by titrating against a standard permanganate solution as follows:

5SO2 + 2MnO4- + 2H2O 5SO42- + 2Mn2+ + 4H+

Calculate the number of grams of SO2 in a sample of air if 7.37 mL of 0.00800 M KMnO4 solution are required for the titration.

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Reactions in Aqueous Solution Student Version