NaCl (aq) + Mg(NO3)2 (aq)  NaNO3 (aq) + MgCl2 (aq) 2 The solubility rules allow us to determine if a double-replacement reaction will actually occur. Consider: 2 NaCl (aq) + Mg(NO3)2 (aq)  NaNO3 (aq) + MgCl2 (aq) 2 Did a reaction actually occur? (Hint: Think about the 5 indicators of chemical change) Energy released Gas evolution Color change Temperature change Precipitate formation No, there is no reaction because all of the ions remain in solution. How about: 2 NaCl (aq) + Pb(NO3)2 (aq)  NaNO3 (aq) + PbCl2 (s) 2 Yes, because a precipitate was formed.

Solubility Rules Soluble (will NOT form ppt’s) All nitrates, acetates, ammonium and Group 1 salts All chlorides, bromides and iodides except Ag, Pb and Hg1+ All fluorides except Group 2, Pb2+, Fe2+ All sulfates except Ca, Sr, Ba, Hg, Pb2+, and Ag Insoluble (WILL form ppts) All carbonates and phosphates except Group 1 and ammonium All hydroxides except Group 1, Sr and Ba All sulfides except Group 1, 2 and ammonium All oxides except Group 1

Using your solubility rules chart predict the products for the following double-replacement reactions. 1. Zn(NO3)2 (aq) + Na2CO3 (aq)  ZnCO3 (s) + 2NaNO3 (aq) 2. Na3PO4 (aq) + (NH4)2CO3 (aq)  NR 3. BaCl2 (aq) + Na2SO4 (aq)  2 NaCl (aq) + BaSO4 (s) The ions that remain in solution (don’t form a precipitate) are called “spectator ions.” In rxn 1, the spectators are Na+1 and NO3-1 In rxn 2, all of the ions are spectators…hence ‘no reaction’ In rxn 3, the spectators are Na+1 and Cl-1

Net Ionic Reactions Something to think about…When you get a paycheck, you’re more interested in the net pay than the overall pay because the net pay is the most inherently interesting. In net ionic reactions, only non-spectator species are actually shown because they’re the only ones doing anything observable. Zn(NO3)2 (aq) + Na2CO3 (aq)  ZnCO3 (s) + 2NaNO3 (aq) Zn+2 (aq) + CO32- (aq)  ZnCO3 (s) 1. Write down the insoluble product, then list the ions that had to form it as reactants. 2. Balance your net ionic reaction and add states of matter. 3. Pat yourself on the back, you’ve just balanced a net ionic rxn. 