4. 2 Continued… Writing Net Ionic Equations Learning Goals: 1 4.2 Continued… Writing Net Ionic Equations Learning Goals: 1. To dissociate all products and reactants (when applicable) 2. To determine the state of reactants and products using solubility rules. 3. To determine spectator ions present in solution

Writing ionic equations Dissociation- to break apart into positive and negative ions A soluble compound will dissociate into ions. An insoluble compound does not dissociate. Precipitate- insoluble solid formed in a reaction. It looks cloudy. http://wps.prenhall.com/esm_brown_chemistry_9/2/671/171787.cw/index.html

Pb(NO3)2(s)  Pb(NO3)2(aq) H2O Pb(NO3)2(s)  Pb(NO3)2(aq) Pb2+(aq) + 2 NO31–(aq) add water dissociation: “splitting into ions” NO31– Pb2+ Pb2+ NO31– NO31–

Solubility Rules Read solubility rule from p.860 of honors chem book Alkali metals and ammonium ions are soluble. Acetates and nitrtaes are soluble. Halogens (except F) with metals (except Ag, Hg, Pb) are soluble. Most sulfates are soluble. Carbonates, hydroxides, oxides, sulfides, and phosphates are insoluble.

AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq) Double Replacement Reaction AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq) Ms. Wrong Mr. Cool Mr. Cool Ms. Wrong Ag+ Sandro Na+ NO3– Cl– Jessica  Ag+ Sandro NO3– Na+ Cl– Jessica

Precipitate? Precipitate?

Ms. Wrong & Mr. Cool are waiting for their matches…

Pb(NO3)2(aq) + 2NaI(aq) g PbI2i+ 2NaNO3(aq) Molecular Equation Total Ionic Equation: Pb2+ + 2NO3- + 2Na+ + 2I- g PbI2i + 2Na+ + 2NO3- Spectator ions appear on both sides of the equation without changing. Net ionic equations ignore spectator ions. Net ionic: Pb2+(aq) + 2I- (aq) g PbI2(s)

For double-replacement reactions, reaction will occur if any product is: water, a gas, a precipitate driving forces _Pb(NO3)2(aq) + _KI(aq)  _PbI2(s) + _KNO3(aq) _KOH(aq) + _H2SO4(aq)  _K2SO4(aq) + _H2O(l)

Try this BaCl2 ( )+ Na2SO4 ( ) 2NaCl ( ) + BaSO4 ( ) Total Ionic Equation: Net Ionic Equation: Spectator Ions: Remember: If each product is soluble, no reaction occurs (NR)

Summary on Double Displacement Rxns Remember!!! Double displacement rxns only happen when 1 of the following is formed: A precipitate is formed A gas is formed Water is formed In all other cases, the ions stay in solution!!! No rxn happens!!! 12