3 Double Displacement Reaction A reaction in which aqueous ionic compounds rearrange cations (A & B) and anions (X & Y), resulting in the formation of new compoundsYX+BAY+XBA
4 Types of Double Displacement Reactions A reaction that forms a solidA reaction that forms a gasA reaction that forms water (neutralization)
5 Determining the Products of a Double Displacement Reaction First determine the ions that make up the reactants.For example, consider the reaction between lithium chloride and lead(II) nitrate:LiCl(aq) + Pb(NO3)2(aq)
6 LiCl(aq) + Pb(NO3)2(aq) Lithium ions, Li+ Chloride ions, Cl- The reactants are composed of four ions:LiCl(aq) + Pb(NO3)2(aq) Lithium ions, Li+Chloride ions, Cl-Lead(II) ions, Pb2+Nitrate ions, NO3-
7 2LiCl(aq) + Pb(NO3)2(aq) 2LiNO3(aq) + PbCl2(s) To determine the products of the reaction, simply change the pairs of ions.2LiCl(aq) + Pb(NO3)2(aq) 2LiNO3(aq) + PbCl2(s)Lithium chloride +lead(II) nitratelithium nitrate + lead(II) chloride
8 MgCl2(aq) + Ca(OH)2(aq) Mg(OH)2(s) + CaCl2(aq) Specific Example:MgCl2(aq) + Ca(OH)2(aq) Mg(OH)2(s) + CaCl2(aq)What “sign” suggests a chemicalreaction has occurred?If there is no precipitate formed,there is NO reaction.How can we predict precipitate formation?
9 When will a double displacement reaction occur? When a precipitate is produced from the reaction of 2 aqueous reactants.To determine which products are precipitates (insoluble in water), you must check your solubility chartWhen a pure liquid is formed – typically water.When a gas is produced (often CO2, H2, and O2)In summary any reaction where the two products are not aqueous!
10 SOLUBILITYA solution is a homogenous mixture of a solute and a solventEvery solute has its own solubility in a given solventSolubility is described as the maximum quantity of a solute that will dissolve in a solvent at a given temperature and pressure e.g. adding NaCl to waterIf a product in a reaction is insoluble a precipitate will formWe use a SOLUBILITY TABLE to determine whether a precipitate will form (Nelsons Chemistry 11 p Table 1)
12 What ions can be used to precipitate the following… Ag+NitrateC2H3O2-Ba2+OH-Phosphate
13 A Reaction That Forms a Solid Precipitate Reactions CaCl2(aq) + Na2CO3(aq) (dissolved) (dissolved) CaCO3(s) + 2 NaCl(aq) (solid precipitate) (dissolved) A precipitate is an insoluble solid that is formed by a chemical reaction between two soluble compounds
14 A Reaction That Forms a Gas Formation of Carbon Dioxide acetic acid + sodium hydrogen carbonate sodium acetate + carbonic acid CH3COOH(aq) + NaHCO3(s) NaCH3COO(aq) + H2CO3(aq) NOT the overall reaction because there is NO carbon dioxide!!!
15 Carbonic acid DECOMPOSES into liquid water and carbon dioxide H2CO3(aq) H2O(l) + CO2(g)OVERALL Reactionacetic acid + sodium hydrogen carbonate sodium acetate + water + carbon dioxideCH3COOH(aq) + NaHCO3(s) NaCH3COO(aq) + H2O(l) + CO2(g)
16 NH4Cl(aq) + NaOH(aq) NaCl(aq) + NH4OH(aq) Formation of Ammoniaammonium chloride + sodium hydroxide sodium chloride + ammonium hydroxideNH4Cl(aq) + NaOH(aq) NaCl(aq) + NH4OH(aq)NOT the overall reaction because NO ammonia!
17 Ammonium hydroxide DECOMPOSES to form water and ammonia ammonium hydroxide water + ammoniaNH4OH(aq) H2O(l) + NH3(g)OVERALL Reactionammonium chloride + sodium hydroxide sodium chloride + water + ammoniaNH4Cl(aq) + NaOH(aq) NaCl(aq) + H2O(l) + NH3(g)
18 A Reaction That Forms Water (Neutralization Reactions) Acid reacts with a BaseProducts are neither acidic or basicmagnesium hydroxide + hydrochloric acid magnesium chloride + waterMg(OH)2(s) + 2HCl(aq) MgCl2(aq) + 2H2O(l)
19 then the products include Summary flowchart to help predict the products of a double displacement reactionIf one reactant…+the other reactant…then the products includeis an aqueous salta precipitateis an acidhas carbonate ionswater andcarbon dioxidehas ammonium ionshas hydroxide ionswater and ammoniawater