Predicting the Products of Double Replacement Reactions Using a Solubility Table

Introduction Double replacement reactions are reactions that occur in solution. Cations and anions change places in double replacement reactions. One product must be: solid (precipitate) insoluble gas water

Basics Double replacement reactions have the following form: AX(aq) + BY(aq) → AY(s) + BX(aq) For example: BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2 NaCl(aq) Pb(NO3)2(aq) + 2 HCl(aq) → PbCl2(s) + 2 HNO3(aq) KOH(aq) + HBr(aq) → H2O(l) + KBr(aq)

BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2 NaCl(aq) Basics In each of these reactions, the cations and anions change partners: BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2 NaCl(aq)

BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2 NaCl(aq) Basics In each of these reactions, the cations and anions change partners: BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2 NaCl(aq)

BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2 NaCl(aq) Basics In each of these reactions, the cations and anions change partners: BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2 NaCl(aq)

Basics Again, one of the products must be: a precipitate (indicated by (s) or ↓) an insoluble gas (indicated by (g) or ↑) water (from the reaction of an acid with a base) We will be looking at those reactions which form (or don’t form) precipitates as products

Solubility Solubility is the ability of a compound, called the solute, to dissolve in a liquid, called the solvent. Different compounds have different solubilities. We are interested in those compounds that are not very soluble. We want to know which ones form precipitates.

Solubility We have a set of guidelines for the solubility of ionic compounds in water. The guidelines tell us whether or not a particular family of ionic compounds is soluble. We can use these guidelines to predict the formation of a participate in a potential double replacement reaction. If no precipitate forms, then there is no reaction.

Solubility Guidelines Most sodium, Na+, potassium, K+, and ammonium, NH4+, compounds are soluble in water. Most nitrate, NO3−, acetate, CH3COO−, and chlorate, ClO3−, compounds are soluble in water. Most chloride, Cl−, compounds are soluble, except those of silver, AgCl, mercury(I), Hg2Cl2, and lead, PbCl2. Lead(II) chloride is soluble in hot water. Most sulfate, SO42−, compounds are soluble, except those of barium, BaSO4, strontium, SrSO4, and lead, PbSO4. Most carbonate, CO32−, phosphate, PO43−, and silicate, SiO32−, compounds are insoluble, except those of sodium, potassium, and ammonium. Most sulfides, S2−, compounds are insoluble, except those of calcium, Ca2+, strontium, Sr2+, sodium, Na+, potassium, K+, and ammonium, NH4+.

Applications Example 1. Predict the result of mixing a solution of lead(II) nitrate with sodium sulfate. Pb(NO3)2(aq) + Na2SO4(aq) Cations Anions Possible precipitates Pb2+ NO3– Na+ SO42– Pb(NO3)2 Pb(NO3)2 PbSO4 Na2SO4 Na2SO4 NaNO3 These are already in solution. We know that two of the possible precipitates are soluble.

Applications Example 1. Predict the result of mixing a solution of lead(II) nitrate with sodium sulfate. Pb(NO3)2(aq) + Na2SO4(aq) Cations Anions Possible precipitates Pb2+ NO3– Na+ SO42– Pb(NO3)2 Next, we look at the solubility guidelines PbSO4 Na2SO4 Most Na+, K+, and NH4+ compounds are soluble in water. NaNO3 NaNO3

Applications Example 1. Predict the result of mixing a solution of lead(II) nitrate with sodium sulfate. Pb(NO3)2(aq) + Na2SO4(aq) Cations Anions Possible precipitates Pb2+ NO3– Na+ SO42– Pb(NO3)2 Next, we look at the solubility guidelines PbSO4 Na2SO4 Most NO3–, CH3COO–, and ClO3– compounds are soluble in water. NaNO3

Applications Example 1. Predict the result of mixing a solution of lead(II) nitrate with sodium sulfate. Pb(NO3)2(aq) + Na2SO4(aq) Cations Anions Possible precipitates Pb2+ NO3– Na+ SO42– Pb(NO3)2 Next, we look at the solubility guidelines PbSO4 Na2SO4 Most Cl– compounds are soluble, except those of Ag+, Hg22+, and Pb2+. NaNO3

Applications Example 1. Predict the result of mixing a solution of lead(II) nitrate with sodium sulfate. Pb(NO3)2(aq) + Na2SO4(aq) Cations Anions Possible precipitates Pb2+ NO3– Na+ SO42– Pb(NO3)2 Next, we look at the solubility guidelines PbSO4 Na2SO4 Most SO42– compounds are soluble, except those of Ba2+, Sr2+, and Pb2+. NaNO3

Applications Example 1. Predict the result of mixing a solution of lead(II) nitrate with sodium sulfate. Pb(NO3)2(aq) + Na2SO4(aq) Cations Anions Possible precipitates Pb2+ NO3– Na+ SO42– Pb(NO3)2 Next, we look at the solubility guidelines PbSO4 Na2SO4 PbSO4 will be a precipitate. NaNO3

Applications Example 1. Predict the result of mixing a solution of lead(II) nitrate with sodium sulfate. Pb(NO3)2(aq) + Na2SO4(aq) Cations Anions Possible precipitates Pb2+ NO3– Na+ SO42– Pb(NO3)2 We now complete the equation. PbSO4 Na2SO4 PbSO4 will be a precipitate. NaNO3

Applications Example 1. Predict the result of mixing a solution of lead(II) nitrate with sodium sulfate. Pb(NO3)2(aq) + Na2SO4(aq) → PbSO4(s) + 2 NaNO3(aq) Cations Anions Possible precipitates Pb2+ NO3– Na+ SO42– Pb(NO3)2 We now complete the equation. PbSO4 Na2SO4 PbSO4 will be a precipitate. NaNO3

Applications Example 2. Predict the result of mixing a solution of copper(II) nitrate with sodium chloride. Cu(NO3)2(aq) + NaCl (aq) Cations Anions Possible precipitates Cu2+ NO3– Na+ Cl– Cu(NO3)2 Cu(NO3)2 CuCl2 NaCl NaCl NaNO3 These are already in solution. We know that two of the possible precipitates are soluble.

Applications Example 2. Predict the result of mixing a solution of copper(II) nitrate with sodium chloride. Cu(NO3)2(aq) + NaCl (aq) Cations Anions Possible precipitates Cu2+ NO3– Na+ Cl– Cu(NO3)2 Cu(NO3)2 Next, we look at the solubility guidelines CuCl2 NaCl NaCl Most Na+, K+, and NH4+ compounds are soluble in water. NaNO3 NaNO3

Applications Example 2. Predict the result of mixing a solution of copper(II) nitrate with sodium chloride. Cu(NO3)2(aq) + NaCl (aq) Cations Anions Possible precipitates Cu2+ NO3– Na+ Cl– Cu(NO3)2 Cu(NO3)2 Next, we look at the solubility guidelines CuCl2 NaCl NaCl Most NO3–, CH3COO–, and ClO3– compounds are soluble in water. NaNO3

Applications Example 2. Predict the result of mixing a solution of copper(II) nitrate with sodium chloride. Cu(NO3)2(aq) + NaCl (aq) Cations Anions Possible precipitates Cu2+ NO3– Na+ Cl– Cu(NO3)2 Cu(NO3)2 Next, we look at the solubility guidelines CuCl2 CuCl2 NaCl NaCl Most Cl– compounds are soluble, except those of Ag+, Hg22+, and Pb2+. NaNO3

Applications Example 2. Predict the result of mixing a solution of copper(II) nitrate with sodium chloride. Cu(NO3)2(aq) + NaCl (aq) Cations Anions Possible precipitates Cu2+ NO3– Na+ Cl– Cu(NO3)2 Cu(NO3)2 Next, we look at the solubility guidelines CuCl2 CuCl2 NaCl NaCl There is no precipitate and no reaction. NaNO3

Applications Example 2. Predict the result of mixing a solution of copper(II) nitrate with sodium chloride. Cu(NO3)2(aq) + NaCl (aq) Cations Anions Possible precipitates Cu2+ NO3– Na+ Cl– Cu(NO3)2 Cu(NO3)2 We now complete the equation. CuCl2 CuCl2 NaCl NaCl There is no precipitate and no reaction. NaNO3

Applications Example 2. Predict the result of mixing a solution of copper(II) nitrate with sodium chloride. Cu(NO3)2(aq) + NaCl (aq) → no reaction Cations Anions Possible precipitates Cu2+ NO3– Na+ Cl– Cu(NO3)2 Cu(NO3)2 We now complete the equation. CuCl2 CuCl2 NaCl NaCl There is no precipitate and no reaction. NaNO3

Practice Problems Predict the result of mixing each of the following solutions. AgNO3(aq) + NaCl(aq) → Cu2SO4(aq) + Na2CO3(aq) → BaCl2(aq) + CuSO4(aq) → Pb(CH3COO)2(aq) + Na3ClO3(aq) → FeCl2(aq) + CaS(aq) → AgCl(s) + NaNO3(aq) CuCO3(s) + Na2SO4(aq) BaSO4(s) + CuCl2(aq) no reaction FeS(s) + CaCl2(aq)