Presentation on theme: "Reactions in Aqueous Solutions"— Presentation transcript:
1Reactions in Aqueous Solutions Chapter 8Reactions in Aqueous Solutions
2Will the reaction occur? Driving forcesForming a solid (“precipitate)Transfer of electronsForming waterForming a gasWill the reaction occur? Yes, if one of the above driving forces happens.
3Dissolving ionsA strong electrolyte completely separates into ions when it is mixed with water.Example: NaClComplete the equation of silver nitrate dissolving in water:AgNO3(s) NaCl(S)Na+(aq) + Cl-(aq)H2O
4PrecipitatesIf you mix NaCl(aq) and AgNO3 (aq) , what possible products could form?NaCl(aq) and AgNO3 (aq) ?The anions (Cl- and NO3-)change places.NaCl(aq) and AgNO3 (aq) NaNO3(aq) + AgCl(s)AgCl is a precipitate, so write an “(s)”A precipitate is an insoluble solid. Insoluble = it cannot dissolve in water.What is the driving force in this reaction?
5Double replacement (continued) A double replacement reaction happens when a precipitate forms.Reactants must be aqueous (dissolved in water)Example: NaCl dissolved would be shown as NaCl(aq)If something is “slightly soluble” it will also make a precipitate, so slightly soluble is almost the same as insoluble. Solubility chart on page 245 will show you when a precipitate will form.
6Example Example: KNO3 Soluble or insoluble? Rule #2: K+ salts are usually soluble.Answer: Soluble (No precipitate)
7Will this double replacement actually happen?? Practice: Will this form a reaction?Write the formulas of the possible products (Inside and outside)Use the solubility chart to determine if any of the products are INSOLUBLE.If one or both products are insoluble, a chemical reaction will happen.
8Examples:KNO3 and BaCl2KOH and Fe(NO3)3Na2SO4 and Pb(NO3)2
10Double ReplacementYou should be able to write three types of chemical equations for double replacement:1. Molecular equation2. Complete ionic equation3. Net ionic equation
11Double ReplacementThe molecular equation shows the complete formulas of all reactants and productsNaCl(aq) + AgNO3 (aq) NaNO3(aq) + AgCl(s)The complete ionic equation shows all strong electrolytes (aq) as ions.Na+(aq) + Cl-(aq) + Ag+(aq) + NO3-(aq)Na+(aq) + NO3-(aq + AgCl(s)
12Double ReplacementThe net ionic equation shows only the chemicals participating in the reaction.Steps:Remove the “spectator ions”Spectator ions are the same on the reactant side and the product side (Na+ and NO3-)Na+(aq) + Cl-(aq) + Ag+(aq) + NO3-(aq)Na+(aq) + NO3-(aq + AgCl(s)Net ionic equation:Cl-(aq) + Ag+(aq) AgCl(s)
13Acid-Base Reactions and Oxidation-Reduction Reactions 8.2Acid-Base Reactions andOxidation-Reduction Reactions
14Arrhenius Acids and Bases An Arrhenius Acid is a substance that produces H+ ions when dissolved in water.A “strong acid” is an acid that is a strong electrolyte. It completely separates into H+ and the anion.HCl H+ + Cl-Strong acids: HCl, HNO3 and H2SO4
15Arrhenius Acids and Bases An Arrhenius Base produces OH ions when dissolved in water.A strong base completely separates into a metal cation and OH-NaOH Na+ + OH-
16Acid-Base ReactionWrite the molecular equation, complete ionic equation and net ionic equation for the reaction of hydrochloric acid and sodium hydroxide.Molecular equationHCl + NaOH H2O + NaClComplete ionic equationH+ +Cl- + Na+ + OH- H2O(l) + Na+ + Cl-Net ionic equationH+ +OH- H2O(l)
17Acid-Base ReactionWhen an acid and base are mixed, the products are always water and a salt.How do you know a reaction happened? The solution will be hot.An acid-base reaction is the reaction of H+ and OH-
18Oxidation ReductionIn an oxidation-reduction reaction, electrons move from one chemical to another.Common reactions:A metal and a nonmetal reactReactions between nonmetals where O2 is a reactant or product.
19Oxidation Reduction Ca(s) + Cl2(g) CaCl2(s) 2 electronsCa(s) + Cl2(g) CaCl2(s)Which chemical is losing electrons? How many electrons?Ca loses two electronsWhich chemical is gaining electrons? How many electrons?Cl gains one electron
20Oxidation Reduction This happens in two steps: Ca Ca2+ + 2e- Cl + e- Cl-Draw a picture of this reaction:Mg(s) + CuCl2(s) Cu(s) + MgCl2(s)Which chemical loses electrons? How many?Which chemical gains electrons? How many?
218.3 Types of reactions & “How do we know IF it will happen?”
22Classifying reactions Looking at a chemical equation, be able to classify it…Based on driving force:1. Precipitation reactions2. Oxidation-reduction reactions3. Acid-base reactionsTypes of oxidation-reduction reactions:1. Combustion reactions2. Synthesis reactions3. Decomposition reactions4. Single Replacement
23Double Replacement AX+BY → AY +BX Each anion changes places with the cation.Example: sodium sulfate + copper (II) chloride
24Single Replacement:A+BX → AX +BA = a metal or group 7 element.B = metal, group 7 element or hydrogenX = anionA replaces B in the BX compound.Example:Zn(s) +2HCl(aq) H2(g) + ZnCl2(aq)
25Synthesis ReactionsSynthesis– 2 or more substances combine to form one, bigger molecule.General formula…Example: Combustion of CaCa + O2 CaO
26Decomposition Reactions Decomposition– one substance splits to form several smaller molecules/atoms.General formula…Example: Breaking water molecules.What equation will it have? (it’s a reaction that results in Hydrogen gas, H2, and Oxygen,O2)Usually requires energy input (heat, electricity, etc), because we are breaking bonds.