Double Displacement Reactions

Non-Redox Reactions Reactants: Zn + I 2 Product: Zn I 2

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Double Displacement Reactions: At the conclusion of our time together, you should be able to: Distinguish between a non-redox and a redox reaction. Recognize a double replacement (D.R.) reaction. Predict the products of a D.R. reaction. Predict whether a D.R. reaction will occur using solubility rules or formation of gas or H 2 O (l) (neutralization reaction).

Non-Redox Reaction The oxidation number (charge) of the ions involved does not change from the reactant to the product side. The oxidation number (charge) of the ions involved does not change from the reactant to the product side. Na 2 SO 4(aq) + CaCl 2(aq)  CaSO 4(s) + 2NaCl (aq) Na 2 SO 4(aq) + CaCl 2(aq)  CaSO 4(s) + 2NaCl (aq) Redox: (the oxidation #’s are changing) Redox: (the oxidation #’s are changing) 2 Fe + 3 Cl 2  2 FeCl 3 2 K (s) + FeCl 2(aq)  Fe (s) + 2 KCl (aq)

Double Replacement Reactions Two things replace each other. Two things replace each other. Reactants must be two ionic compounds or acids. Reactants must be two ionic compounds or acids. Usually in aqueous solution Usually in aqueous solution Na 2 SO 4(aq) + CaCl 2(aq)  Na 2 SO 4(aq) + CaCl 2(aq)  The positive ions change place. The positive ions change place. Na 2 SO 4(aq) + CaCl 2(aq)  Ca +2 SO Na +1 Cl -1 Na 2 SO 4(aq) + CaCl 2(aq)  Ca +2 SO Na +1 Cl -1 Na 2 SO 4(aq) + CaCl 2(aq)  CaSO 4(s) + 2NaCl (aq) Na 2 SO 4(aq) + CaCl 2(aq)  CaSO 4(s) + 2NaCl (aq)

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To Double Replace or Not to Double Replace? That is the Question? Will only happen if one of the products Will only happen if one of the products doesn’t dissolve in water and forms an insoluble solid (s), precipitate (ppt or ). doesn’t dissolve in water and forms an insoluble solid (s), precipitate (ppt or ). or is a gas that bubbles out. or is a gas that bubbles out. or water forms, H 2 O (neutralization reaction). or water forms, H 2 O (neutralization reaction).

Predicting the Precipitate Insoluble salt = a precipitate Insoluble salt = a precipitate Solubility rules Solubility rules (see handout for explanation) (see handout for explanation) CASH N GiAm

Solubility Rules Practice Predict whether each of the following will be soluble (aq) or an insoluble ppt. (s): KCl KCl Na 2 SO 4 Na 2 SO 4 CaSO 4 CaSO 4 AgSO 4 AgSO 4 Na 2 CO 3 Na 2 CO 3 MgS MgS aq aq s s s

Double Replacement Reactions Double Replacement Reactions occur when a metal replaces a metal in a compound and a nonmetal replaces a nonmetal in a compound Double Replacement Reactions occur when a metal replaces a metal in a compound and a nonmetal replaces a nonmetal in a compound Compound + compound  compound+ compound Compound + compound  compound+ compound AB + CD  AD + CB AB + CD  AD + CB

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Double Replacement Reactions Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together Example: Example: AgNO 3(aq) + NaCl (s)  AgCl (s) + NaNO 3(aq) AgNO 3(aq) + NaCl (s)  AgCl (s) + NaNO 3(aq) Another example: Another example: K 2 SO 4(aq) + Ba(NO 3 ) 2(aq)  KNO 3(aq) + BaSO 4(s) 2

Double Displacement Reactions: Let’s see if you can: Distinguish between a non-redox and a redox reaction. Recognize a double replacement (D.R.) reaction. Predict the products of a D.R. reaction. Predict whether a D.R. reaction will occur using solubility rules or formation of gas or H 2 O (l) (neutralization reaction).

3 Driving Forces for Double Replacement Reactions Water Forms Gas Forms Solid Forms If one of the above is not a product, there will be no reaction.

Double Replacement Two elements in reactants take the place of each other AB + CD  AD + CB AgNO 3(aq) + NaCl (aq)  AgCl (s) + NaNO 3(aq) Zn(OH) 2(aq) + 2HCl (aq)  ZnCl 2(aq) + 2H 2 O (l)

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Practice Predict the products. Balance the equation Predict the products. Balance the equation 1. HCl (aq) + AgNO 3 (aq)  2. CaCl 2 (aq) + Na 3 PO 4 (aq)  3. Pb(NO 3 ) 2(aq) + BaCl 2 (aq)  4. FeCl 3 (aq) + NaOH (aq)  5. H 2 SO 4 (aq) + NaOH (aq)  6. KOH (aq) + CuSO 4 (aq)  7. Ba(NO 3 ) 2(aq) + K 2 CrO 4 (aq)  8. Demo Time!! AgCl + HNO 3 NaCl + Ca 3 (PO 4 ) 2 Ba(NO 3 ) 2 + PbCl 2 NaCl + Fe(OH) 3 Na 2 SO 4 + H 2 O Cu(OH) 2 + K 2 SO 4 BaCrO 4 + KNO 3

Learning Check Which of the following reactions is double replacement? A. 2Al (s) + 3H 2 SO 4(aq)  Al 2 (SO 4 ) 3(aq) + 3H 2(g) B. Na 2 SO 4(aq) + 2AgNO 3(aq)  Ag 2 SO 4(s) + 2NaNO 3(aq) C. 3C (s) + Fe 2 O 3(s)  2Fe (g) + 3CO (g)

Complete and Net Ionic Equations

Reactants: Zn + I 2 Product: Zn I 2

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Complete and Net Ionic Equations: At the conclusion of our time together, you should be able to: 1.Define molecular, complete and net ionic equations 2.Write molecular, complete and net ionic equations 3. Identify a neutralization reaction 4. Realize that this is one of the 5 basic types of chemical reactions

Complete & Net Ionic Equations Many reactions occur in water- that is, in aqueous solution Many reactions occur in water- that is, in aqueous solution Many ionic compounds “dissociate”, or separate, into cations and anions when dissolved in water Many ionic compounds “dissociate”, or separate, into cations and anions when dissolved in water Now we can write a complete ionic equation & net ionic equation. Now we can write a complete ionic equation & net ionic equation.

Complete Ionic Equations Once you write the molecular equation, you should check for reactants and products that are soluble or insoluble. Once you write the molecular equation, you should check for reactants and products that are soluble or insoluble. We usually assume the reaction is in water We usually assume the reaction is in water We can use a solubility table to tell us what compounds dissolve in water. We can use a solubility table to tell us what compounds dissolve in water. If the compound is soluble (does dissolve in water), then split the compound into its component ions If the compound is soluble (does dissolve in water), then split the compound into its component ions If the compound is insoluble (does NOT dissolve in water), then it remains as a compound If the compound is insoluble (does NOT dissolve in water), then it remains as a compound

Solubility Table

Solubilities Not on the Table! Gases will only slightly dissolve in water Gases will only slightly dissolve in water Strong acids and bases dissolve in water Strong acids and bases dissolve in water Hydrochloric, Hydrobromic, Hydroiodic, Hydrochloric, Hydrobromic, Hydroiodic, (All Binaries) (All Binaries) Nitric, Sulfuric, Perchloric Acids Nitric, Sulfuric, Perchloric Acids (Ternary Acids with 2 more O than H) (Ternary Acids with 2 more O than H) Group I hydroxides Group I hydroxides Water slightly dissolves in water! (H+ and OH-) Water slightly dissolves in water! (H+ and OH-)

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Complete Ionic Equation Example: Example: AgNO 3(aq) + NaCl (aq)  AgCl (s) + NaNO 3(aq) 1. This is the full equation (molecular equation) 2. Now write it as an complete ionic equation Anything (aq) will dissociate (separate into ions) Anything (aq) will dissociate (separate into ions) Ag + + NO Na + + Cl -  AgCl (s) + Na + + NO 3 -

Net Ionic Equation Complete ionic equation: Ag + + NO Na + + Cl -  AgCl (s) + Na + + NO Can be simplified by eliminating ions not directly involved in making the reaction happen (spectator ions) = net ionic equation Ag + + Cl -  AgCl (s) Na + and NO 3 - are spectator ions and are removed in the net ionic equation.

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Try Again: Complete Ionic Equations Molecular Equation: K 2 CrO 4(aq) + Ba(NO 3 ) 2(aq)  BaCrO 4(s) + 2 KNO 3(aq) Soluble Soluble Insoluble Soluble Soluble Soluble Insoluble Soluble Complete Ionic Equation: 2 K + + CrO Ba NO 3 -  BaCrO 4 (s) + 2 K NO 3 -

Net Ionic Equations These are the same as complete ionic equations, but you should cancel out ions that appear on BOTH sides of the equation These are the same as complete ionic equations, but you should cancel out ions that appear on BOTH sides of the equation Complete Ionic Equation: 2 K + + CrO Ba NO 3 -  2 K + + CrO Ba NO 3 -  BaCrO 4 (s) + 2 K NO 3 - Net Ionic Equation: CrO Ba +2  BaCrO 4 (s) Spectator Ion

Neutralization Reaction Acid + Base  Salt + Water Molecular Equation: HCl + NaOH  NaCl + H 2 O SolubleSoluble Soluble Molecular SolubleSoluble Soluble Molecular Complete Ionic Equation: H + + Cl - + Na + + OH -  H + + Cl - + Na + + OH -  H 2 O ( l ) + Na + + Cl - H 2 O ( l ) + Na + + Cl -

Net Ionic Equation for Neutralization Reactions These are the same as complete ionic equations, but you should cancel out ions that appear on BOTH sides of the equation These are the same as complete ionic equations, but you should cancel out ions that appear on BOTH sides of the equation Complete Ionic Equation: H + + Cl - + Na + + OH -  H + + Cl - + Na + + OH -  H 2 O ( l ) + Na + + Cl - H 2 O ( l ) + Na + + Cl - Net Ionic Equation: H + + OH -  H 2 O ( l )

Complete Ionic Equations: Let’s see if you can: 1.Define molecular, complete and net ionic equations 2.Write molecular, complete and net ionic equations 3. Identify a neutralization reaction 4. Realize that this is one of the 5 basic types of chemical reactions

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Practice Quiz Net Ionic Equations Write the molecular, complete ionic, and net ionic equations for this reaction: Silver nitrate reacts with calcium chloride Write the molecular, complete ionic, and net ionic equations for this reaction: Silver nitrate reacts with calcium chlorideMolecular: 2AgNO 3 + CaCl 2  2AgCl + Ca(NO 3 ) 2 Complete Ionic: 2Ag + + 2NO Ca Cl -  2AgCl + Ca NO 3 - Net Ionic: 2Ag + + 2Cl -  2AgCl

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