Chapter 7 Chemistry Notes

Generally soluble double displacement ab cd ad cb

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Unformatted text preview: e Stuff, A + B AB) Decomposition (Destroy Stuff, AB A + B) Single Displacement (A + BC AC + B) Precipitation Reactions Br–, I– SO42– none Ag+, Hg2 2+, Pb2+ Ca2+, Sr2+, Ba2+, Pb2+ For example, KI, Pb(NO3)2 , and FeSO4 are soluble (electrolytes), but PbI2, CaSO4 , and AgBr are insoluble solids (none electolytes). Complete (or Total) Ionic Equation 2 KI(aq) + Pb(NO3)2(aq) → 2 KNO3(aq) + PbI2(s) So far the reactions have been written in a “molecular style” where each compound is neutral. For example: 2 KI(aq) + Pb(NO3)2(aq) → 2 KNO3(aq) + PbI2(s). + Mix Intermediate state However, we know that ionic compounds dissociate in solution to form ions: The , KI and Pb(NO3)2 salts dissolve but when Pb2+ cations encounter I- anions a ppt forms. KNO3 (aq) K+(aq) + NO3-(aq) The complete ionic equation shows all ions explicitly. ppt = a precipitate (solid) KI(aq) K+(aq) + I-(aq) Pb(NO3)2 (aq) Pb2+(aq) + 2 NO3-(aq) 2 K+(aq) + 2 I-(aq) + Pb2+(aq) + 2 NO3-(aq) 2 K+(aq) + 2 NO3-(aq) + PbI2(s). Notice: some ions are repeated exactly on left and right…. 4 9/27/2013 Precipitation Reaction: The Movie The Net Ionic Equation • In mixed electrolyte solutions, ions diffuse in the solution. If appropriate “partners” encounter each other they ppt. • Soluble ions remain in solution (as spectators) • Concentration can impact solubility The net ionic equation is obtain from the complete ionic equation by crossing out the “spectator” ions. Spectator ions do not participate (do not change). Rather than write them twice, we simply leave them out. 2 K+(aq) + 2 I-(aq) + Pb2+(aq) + 2 NO3-(aq) 2 K+(aq) + 2 NO3-(aq) + PbI2(s). Net ionic eqn: 2 I-(aq) + Pb2+(aq) PbI2(s). Na+ Spectator Ions Net ionic equations only contain chemical species that change states going from reactants to products. (Notice both atoms and total charge balance.) Cl- MgCO3 Soluble Li+, Na+, K+, NH4+ NO3-, C2H3O2Cl-, Br-, I- (except Hg22+, Ag+, Pb2+) SO42(except Group 2A & Pb2+) Mostly Insoluble (Except Li+, Na+, K+, NH4+, H+) S2- , PO43CO32-(except Group 2A) OH- (slightly soluble Group 2A) 2A) (slightly soluble Group CO , PO Group 2A) S2- 32-(except43- MgCl2 (aq) + Na2CO3 (aq) ----> 2NaCl (aq) + MgCO3(s) does not dissolve. sodium sulfate and barium chloride Writing Precipitation Reactions Molecular Equation: Molecular style Na2SO4 (aq) + BaCl2 (aq) ----> NaCl (aq) + BaSO4 (s) MgCl2(aq) + Na2CO3((aq)2NaCl(aq) + MgCO3(s) Complete Ionic Equation Mg2+(aq)+ 2 Cl-(aq)+ 2 Na+(aq) + CO32-(aq) 2 Na+(aq) + 2 Cl-(aq)+ MgCO3(s) Spectators Advice: by the exam this step should be “doable in your head.” Net Ionic Equation (Eliminate Spectators) Complete Ionic 2Na+ (aq) + SO4 2- (aq) + Ba 2+ (aq) + 2Cl- (aq) ----> 2Na+ (ag) + 2Cl (aq) + BaSO4 (s) Net Ionic Ba2+ (aq) Mg2+(aq)+CO32-(aq) MgCO3(s) Chapter Outline • • • Chemical Equations: Quest for Balance √ Solubility and electrolytes √ Types of Reactions: (by types of chemistry) • • • • • Precipitation & Solubility ◄ Acid-Base (H+, OH-) Gas Evolution (Bubbles) Oxidation-Reduction (Redox, electrons) Types of Reactions: (by atom exchange pattern) • • • • Synthesis (Make Stuff, A + B AB) Decomposition (Destroy Stuff, AB A + B) Single Displacement (A + BC AC + B) Double Displacement (AB + CD AD + CB) ◄ Double Displacement Soluble Li+, Na+, K+, NH4+ NO3-, C2H3O2Cl-, Br-, I- (except Hg22+, Ag+, Pb2+) 2+ SO42atoms do, t(except Group 2Ais Pb ) he answer & Mostly Insoluble If we describe this...
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This note was uploaded on 02/04/2014 for the course CHEM 004:007 taught by Professor Russellarsen during the Fall '13 term at University of Iowa.

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