Ch 09 Notes - Honors Chemistry

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Ch 09 Notes - Honors Chemistry

11/9/2011Tips for Double-replacement ReactionsPredicting the Products ofDouble-replacement Reactions• Formation of water (reaction between an acidand a base)– Example: Ca(OH) 2 + 2 HCl CaCl 2 + 2 H 2 O• Reactions of soluble salts yield an insolublesalt and another soluble salt– Example:2 NaOH(aq) + CuCl 2 (aq) 2 NaCl(aq) + Cu(OH) 2 (s)Predicting the Products ofDouble-replacement Reactions• Reaction of soluble salts yield an insoluble gasand another soluble salt– Example: 2HI(aq) + Li 2 S(aq) H 2 S(g) + 2LiI(aq)• VideoGroup 1 Metals and WaterCombustion Reactions• In a combustion reaction, oxygen combineswith a substance and releases energy in theform of heat and light– Generic: C x H y + O 2 CO 2 + H 2 O– Example: CH 4 + 2 O 2 CO 2 + 2 H 2 O• Usually a hydrocarbon (compound composedof only hydrogen and carbon) but could becarbon or hydrogen as well6


11/9/2011Hydrocarbons• Alkanes are the simplest hydrocarbons– Generic Formula: C n H 2n+2• Methane: CH 4• Ethane: C 2 H 6• Propane: C 3 H 8• Butane: C 4 H 10• Pentane: C 5 H 12• 5 or more carbons use standard prefixesSection 9.3Double-displacement reactions occur between substances in aqueoussolutions and produce precipitates, water, or gases.REACTIONS IN AQUEOUSSOLUTIONSAqueous Solutions• An aqueous solution (aq) contains one ormore substances (solutes) dissolved in water(solvent)– Some molecular solutes exist as molecules insolution• Sucrose, ethanolAqueous Solutions• Some molecular solutes form ions in solution– Hydrogen chloride, acids (form H + in solution)– HCl(aq) H + (aq) + Cl - (aq)Aqueous Solutions• When an ionic compound dissolves in water,its ions can separate (dissociation)– NaCl, CuCl 2 , NaOH– NaCl(s) Na + (aq) + Cl - (aq)Reactions in Aqueous Solutions• When two aqueous solutions that contain ionsare combined, the ions might react with oneanother (always a double-replacement reaction)– Water (solvent) usually will not react• Three types of products can form from thedouble-replacement reaction– A precipitate– Water– A gas7


11/9/2011Reactions that Form PrecipitatesComplete Ionic Equation• Aqueous copper(II) chloride is added to aqueoussodium hydroxide2NaOH(aq) + CuCl 2 (aq) 2NaCl(aq) + Cu(OH) 2 (s)• In a complete ionic equation, all of theparticles are shown as they exist in solution– Soluble ionic compounds are shown as separatedions– Insoluble ionic compounds are shown as solidprecipitates2Na + (aq) + 2OH - (aq) + Cu 2+ (aq) + 2Cl - (aq) 2Na + (aq) + 2Cl - (aq) + Cu(OH) 2 (s)Net Ionic Equation• The ions that do not participate in thereaction are called spectator ions• In a net ionic equation, only the particles thatparticipate in the reaction are shown (nospectator ions)2OH - (aq) + Cu 2+ (aq) Cu(OH) 2 (s)Ionic Equations• Write the formula equation for the reaction ofaqueous potassium chloride with aqueous silvernitrateKCl(aq) + AgNO 3 (aq) AgCl(s) + KNO 3 (aq)• Write the complete ionic equation.K + (aq) + Cl - (aq) + Ag + (aq) + NO 3- (aq) AgCl(s) + K + (aq) + NO 3- (aq)• Write the net ionic equation.Cl - (aq) + Ag + (aq) AgCl(s)Reactions that Form Water• Called a neutralization reaction because anacid (H + ) reacts with a base (OH - )– No evidence of a chemical reaction is observedbecause water is the solvent as well• Hydrobromic acid (HBr) reacts with sodiumhydroxide solutionWhat is the net ionic equation?HBr(aq) + NaOH(aq) H 2 O(l) + NaBr(aq)H + (aq) + Br - (aq) + Na + (aq) + OH - (aq) H 2 O(l) + Na + (aq) + Br - (aq)H + (aq) + OH - (aq) H 2 O(l)HBr(aq) + NaOH(aq) H 2 O(l) + NaBr(aq)8


11/9/2011Ionic EquationsReactions that Form Gases• Write the formula equation for the reaction ofhydrochloric acid and aqueous lithium hydroxideHCl(aq) + LiOH(aq) H 2 O(l) + LiCl(aq)• Write the complete ionic equationH + (aq) + Cl - (aq) + Li + (aq) + OH - (aq) H 2 O(l) + Li + (aq) + Cl - (aq)• Write the net ionic equationH + (aq) + OH - (aq) H 2 O(l)• A gas often bubbles out (like a precipitate) of adouble displacement reaction• Gases commonly formed in reactions:– Carbon dioxide, CO 2– Hydrogen cyanide, HCN– Hydrogen sulfide, H 2 S• Carbonic acid (H 2 CO 3 ) decomposes into waterand carbon dioxideReactions that Form Gases• Hydroiodic acid (HI) reacts with an aqueoussolution of lithium sulfide2HI(aq) + Li 2 S(aq) H 2 S(g) + 2LiI(aq)What is the net ionic equation?2HI(aq) + Li 2 S(aq) H 2 S(g) + 2LiI(aq)2H + (aq) + 2I - (aq) + 2Li + (aq) + S 2- (aq) H 2 S(g) + 2Li + (aq) + 2I - (aq)2H + (aq) + S 2- (aq) H 2 S(g)Ionic Equations• Write the formula equation for the reaction ofhydrochloric acid and sodium sulfide2HCl(aq) + Na 2 S(aq) H 2 S(g) + 2NaCl(aq)• Write the complete ionic equation2H + (aq) + 2Cl - (aq) + 2Na + (aq) + S 2- (aq) H 2 S(g) + 2Na + (aq) + 2Cl - (aq)• Write the net ionic equation2H + (aq) + S 2- (aq) H 2 S(g)9

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