Non-redox Reactions/ Double Replacement Reactions OBJECTIVES: 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 H2O(l) (neutralization reaction). Complete and balance any D.R. that will occur. Write complete ionic and net ionic reactions.

Non-redox Reaction The oxidation number (charge) of the ions involved does not change from the reactant to the product side. Na2SO4(aq) + CaCl2(aq) ® CaSO4(s) + 2NaCl(aq) Redox: (the oxidation #’s are changing) 2 Fe + 3 Cl2  2 FeCl3 2 K(s) + FeCl2(aq)  Fe(s) + 2 KCl(aq)

Double Replacement Two things replace each other. Reactants must be two ionic compounds or acids. Usually in aqueous solution Na2SO4(aq) + CaCl2(aq) ® The positive ions change place. Na2SO4(aq)+ CaCl2(aq)®Ca+2 SO42- + Na+1Cl-1 Na2SO4(aq) + CaCl2(aq) ® CaSO4(s) + 2NaCl(aq)

To Double Replace or Not to Double Replace? That is the Question? Will only happen if one of the products doesn’t dissolve in water and forms an insoluble solid (s), precipitate (ppt). or is a gas that bubbles out. or water forms, H2O (neutralization reaction).

Predicting the Precipitate Insoluble salt = a precipitate Solubility rules (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 Na2SO4 CaSO4 AgSO4 Na2CO3 MgS

Solubility Rules Practice KCl(aq) Na2SO4(aq) CaSO4(s) AgSO4(s) Na2CO3(aq) MgS(s)

Complete & Net Ionic Equations Many reactions occur in water- that is, in aqueous solution 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.

Complete Ionic Equation Example: AgNO3(aq) + NaCl (aq)  AgCl (s) + NaNO3(aq) this is the full equation (molecular equation) 2. now write it as an complete ionic equation Anything (aq) will dissociate (separate into ions) Ag+ + NO3- + Na+ + Cl-  AgCl(s) + Na+ + NO3-

Net Ionic Equation Ag+ + Cl-  AgCl(s) Complete ionic equation: Ag+ + NO3- + Na+ + Cl-  AgCl(s) + Na+ + NO3- 3. 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 NO3- are spectator ions and are removed in the net ionic equation.

Double Replacement Two elements in reactants take the place of each other AB + CD  AD + CB AgNO3(aq)+ NaCl(aq) AgCl(s) + NaNO3(aq) Zn(OH)2(aq) + 2HCl(aq)  ZnCl2(aq) + 2H2O(l)

Learning Check Which of the following reactions is double replacement? A. 2Al(s) + 3H2SO4(aq)  Al2(SO4)3(aq) + 3H2(g) B. Na2SO4(aq) + 2AgNO3(aq)Ag2SO4(s)+ 2NaNO3(aq) C. 3C(s) + Fe2O3(s)  2Fe(g) + 3CO(g)

Double Replacement Will only happen if one of the products doesn’t dissolve in water and forms an insoluble solid (s), precipitate (ppt). or is a gas that bubbles out. or water forms, H2O (neutralization reaction).