Presentation on theme: "Reactions in Aqueous Solution"— Presentation transcript:
1 Reactions in Aqueous Solution Chapter 4 – Part 2
2 QuestionWhat makes things work?Why do substances do what they do?
3 Precipitation Reactions Insoluble Solid Formation From the Mixing of Two Solutions
4 Precipitation Reactions When one mixes two solutions containing ions that form compounds that are insoluble, a precipitate is formed.Why do they do that?
5 Solubility Rules for Common Ionic Compounds In water at 250C Soluble CompoundsExceptionsCompounds containing alkali metal ions and NH4+NoneNO3-, HCO3-, ClO3-Cl-, Br-, I-Halides of Ag+, Hg22+, Pb2+SO42-Sulfates of Ag+, Ca2+, Sr2+, Ba2+, Hg2+, Pb2+Insoluble CompoundsCO32-, PO43-, CrO42-, S2-OH-Compounds containing alkali metal ions and Ba2+4.2
6 AgNO3 (aq) + KCl (aq) AgCl (s) + KNO3 (aq) Molecular EquationThe molecular equation lists the reactants and products in their molecular form.AgNO3 (aq) + KCl (aq) AgCl (s) + KNO3 (aq)
7 Ionic EquationIn the ionic equation all strong electrolytes (strong acids, strong bases, and soluble ionic salts) are dissociated into their ions.This more accurately reflects the species that are found in the reaction mixture.Ag+ (aq) + NO3- (aq) + K+ (aq) + Cl- (aq) AgCl (s) + K+ (aq) + NO3- (aq)
8 Writing Net Ionic Equations Write a balanced molecular equation.Dissociate all strong electrolytes.Cross out anything that remains unchanged from the left side to the right side of the equation.Write the net ionic equation with the species that remain.
9 Precipitation Reactions precipitatePb(NO3)2 (aq) + 2NaI (aq) PbI2 (s) + 2NaNO3 (aq)molecular equationionic equationnet ionic equation____________ are spectator ions4.2
10 Gravimetric Analysis Dissolve unknown substance in water React unknown with known substance to form a precipitateFilter and dry precipitateWeigh precipitateUse chemical formula and mass of precipitate to determine amount of unknown ion4.6
11 Electron Transfer Reactions Oxidation ReductionElectron Transfer Reactions
12 Oxidation-Reduction Reactions If a substance gives up electrons, something must have collided with that substance and accepted the electrons.Why do they do that?
13 Displacement Reactions In displacement reactions, ions oxidize or reduce an element.The ions, then, are reduced or oxidized.
14 Displacement Reactions In this reaction,silver ions oxidizecopper metal.Cu (s) + 2 Ag+ (aq) Cu2+ (aq) + 2 Ag (s)
15 Displacement Reactions The reverse reaction,however, does notoccur.Cu2+ (aq) + 2 Ag (s) Cu (s) + 2 Ag+ (aq)x
17 Oxidation-Reduction Reactions (electron transfer reactions)2Mg (s) + O2 (g) MgO (s)Oxidation half-reaction (lose e-)Reduction half-reaction (gain e-)4.4
18 Zn (s) + CuSO4 (aq) ZnSO4 (aq) + Cu (s) AgentsZn (s) + CuSO4 (aq) ZnSO4 (aq) + Cu (s)___ is oxidized___ is the reducing agent____ is reduced___ is the oxidizing agent4.4
19 Copper wire reacts with silver nitrate to form silver metal. What is the oxidizing agent in the reaction?___ is reduced___ is the oxidizing agent4.4
20 Oxidation NumbersTo determine if an oxidation-reduction reaction has occurred, we assign an oxidation number to each element in a neutral compound or charged entity.Review the rules on calculating an oxidation number for atoms in a compound.
21 Types of Oxidation-Reduction Reactions Combination ReactionA + B CS + O SO2Decomposition ReactionC A + B2KClO KCl + 3O24.4
22 Types of Oxidation-Reduction Reactions Displacement ReactionA + BC AC + BSr + 2H2O Sr(OH)2 + H2TiCl4 + 2Mg Ti + 2MgCl2Cl2 + 2KBr KCl + Br24.4
23 Types of Oxidation-Reduction Reactions Disproportionation ReactionElement is simultaneously oxidized and reduced.Cl2 + 2OH ClO- + Cl- + H2O4.4
24 Ca2+ + CO32- CaCO3 NH3 + H+ NH4+ Zn + 2HCl ZnCl2 + H2 Ca + F2 CaF2 Classify the Following ReactionsCa2+ + CO CaCO3NH3 + H NH4+Zn + 2HCl ZnCl2 + H2Ca + F CaF24.4
25 Balancing Equations That Cannot be Balanced by Inspection Oxidation ReductionBalancing Equations That Cannot be Balanced by Inspection
26 Balancing Redox Equations Break into Half ReactionsBalance Half ReactionsBalance all but H,OBalance O with waterBalance H with H+Balance charge with e-Add Half Reactions TogetherPractice Due 10/09/ AM