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Double Replacement Reactions. DR rxns occur in aqueous solutions. What happens when substances dissolve in water?. depends if substance is ionic or covalent. Dissolving. c ovalent substances (such as sugar can dissolve but molecules stay intact in solution)
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DR rxns occur in aqueous solutions • What happens when substances dissolve in water? • depends if substance is ionic or covalent
Dissolving • covalent substances (such as sugar can dissolve but molecules stay intact in solution) • C6H12O6(s) C6H12O6(aq) • covalent substances: moleculesspread out in solution
Dissolving • Ionic substances ionize (dissociate) when dissolve; molecules do not remain intact • NaCl(s) Na+1(aq) + Cl-1(aq) • Ionic substances: ions spread out in solution
Double Replacement Reactions • occur when mix 2 ionic compounds together in an aqueous soln • 3 possible products: - liquid (H2O) - gas - solid
Reactions that form liquid water HBr(aq) + NaOH(aq) H2O(l) + NaBr(aq) aqueous refers to something dissolved in water so when water is a product it is labeled as liquid NOT aqueous
H2O(l) + CO2(g) Reactions that form Gases HCl(aq) + NaHCO3(aq) H2CO3(aq) + NaCl(aq) HCl(aq) + NaHCO3(aq) H2O(l) + CO2(g) + NaCl(aq)
Reactions producing Solids 2 NaOH(aq) + CuCl2(aq) 2 NaCl(aq) + Cu(OH)2(s)
Reactions producing Solids Precipitation reactions: • occur when an insoluble solid is formed as a result of chemical reaction solid precipitate forms - opposite of dissolving!
So how do you know if a product of a DR reaction is aqueous or a solid, liquid or gas? Table F is used to determine if a product is soluble or not If soluble: (aq) If not soluble: (s)
Complete Ionic Equations and Net Ionic Equations
Complete Ionic Equations show all ions involved in a chemical reaction taking place in aqueous solution
Ex: Complete Ionic Equation NaOH(aq) + CuCl2(aq) 2 NaCl(aq) + Cu(OH)2(s) Na+1(aq) + 2OH-1(aq) + Cu2+(aq) + 2Cl-1(aq) 2Na+1(aq) + 2Cl-1(aq) + Cu(OH)2(s)
Net Ionic Equationsshow only the ions that form a non-aqueous product in a DR chemical reaction
Net ionic equation: 2OH-1(aq) + Cu2+(aq) Cu(OH)2(s) Solid as product Complete ionic equation: 2Na+1(aq) + 2OH-1(aq) + Cu2+(aq) + 2Cl-1(aq) 2Na+1(aq) + 2Cl-1(aq) + Cu(OH)2(s) • Notice some ions do not participate in reaction • known as spectator ions • cross out spectator ions to get net ionic equation
Net ionic equation: H+1(aq) + OH-1(aq) H2O(l) Water as product HBr(aq) + NaOH(aq) H2O(l) + NaBr(aq) Complete ionic equation: H+1(aq) + Br-1(aq) + Na+1(aq) + OH-1(aq) H2O(l) + Na+1(aq) + Br-1(aq)
Net ionic equation: H+1(aq) + HCO3-1(aq) H2O(l) + CO2(g) Gases as product HCl(aq) + NaHCO3(aq) H2O(l) + CO2(g) + NaCl(aq) Complete ionic equation: H+1(aq) + Cl-1(aq) + Na+1(aq) + HCO3-1(aq) H2O(l) + CO2(g) + Na+1(aq) + Cl-1(aq)
Conservation of Charge total charge (reactant side) must = total charge on product side