= cations (+) = anions (-) Ions in Aqueous Solution Pb(NO3)2(s) Pb(NO3)2(aq) Pb2+(aq) + 2 NO31–(aq) Pb2+ NO31– Pb2+ NO31– add water dissociation: “splitting into ions” NaI(s) NaI(aq) Na1+(aq) + I1–(aq) add water Na1+ I1– Na1+ I1– = cations (+) = anions (-)

= cations (+) = anions (-) NR For double-replacement rxns(or precipitate rxns), The reaction will occur if any product is: water a gas a precipitate driving forces Check new combinations to decide! = cations (+) = anions (-) _ Pb(NO3)2(aq) + _ K2SO4(aq) 1 1 1 _ PbSO4(s) + _ KNO3(aq) 2 Pb2+ NO31– K1+ SO42- Pb2+ SO42- (?) K1+ NO31– (?) (ppt) (aq) _ FeCl3(aq) + _ Cu(NO3)2(aq) NR Fe3+ NO31– (?) Cl1– Cu2+ (?) Fe3+ Cl1– Cu2+ NO31– (aq) (aq)

= cations (+) = anions (-) precipitate: a solid product that forms in an aqueous reaction SPECTATOR IONS = cations (+) = anions (-) Na2CO3(aq) + Ca(NO3)2 (aq) CaCO3(s) + 2NaNO3(aq) 2Na1+(aq) + CO32– (aq) + Ca2+(aq) + 2NO31–(aq) COMPLETE IONIC EQUATION CaCO3(s) + 2Na1+ (aq) + 2NO31–(aq) NET IONIC EQUATION CO32– (aq) + Ca2+(aq) CaCO3(s) clear Na2CO3 solution clear Ca(NO3)2 solution cloudy solution containing CaCO3(s) and NaNO3(aq)

Mix together ZnSO4(aq) and BaCl2(aq): clear ZnSO4 solution clear BaCl2 solution ZnSO4 (aq) BaCl2(aq) Zn2+(aq) + SO42- (aq) Ba2+(aq) + 2 Cl1–(aq) Ba2+ Cl1– Zn2+ SO42-

Mix them and get the complete ionic equation… __Zn2+(aq) + __SO42–(aq) + __Ba2+(aq) + __Cl1–(aq) 1 1 1 2 yields ppt __BaSO4 (s) 1 + __Zn2+(aq) + __Cl1-(aq) 1 2 Cl1– Zn2+ Ba2+ SO42- Cl1– Cancel spectator ions to get net ionic equation… __Ba2+(aq) + __SO42– aq) 1 1 __BaSO4(s) 1 Ba2+ SO42- Ba2+ SO42-

= In a reaction: atoms are rearranged mass AND energy are conserved charge Balancing Chemical Equations law of conservation of mass same # of atoms of each type on each side of equation =

Reaction Conditions and Terminology Certain symbols give important info about a reaction. (s) = solid (l) = liquid (g) = gas (aq) = aqueous (dissolved in H2O) NaCl(s) NaCl(aq) More on aqueous… -- “soluble” or “in solution” also indicate that a substance is dissolved in water (usually)

(i.e., clues about the reaction) Other symbols… (i.e., clues about the reaction) means... “yields” or “produces” means ______ is added to the reaction heat MgCO3(s) MgO(s) + CO2(g) Temp. at which we perform rxn. might be given. 400oC C6H5Cl + NaOH C6H5OH + NaCl The catalyst used might be given. C2H4(g) + H2(g) C2H6(g) Pt

= cations (+) = anions (-) How do we know if a reaction will occur? Li Na Mg Al Zn Fe Pb H+ Cu Hg Ag Au For single-replacement rxns, use Activity Series. Elements above replace elements below. = cations (+) = anions (-) _ Ca(s) + _ FeSO4 1 1 1 _ Fe (s) + _ CaSO4 (aq) 1 _ Pb(s) + _ Al2O3 (aq) No Reaction _ Cl2(g) + _ MgBr2(aq) 1 1 _ Br2 (g) + _ MgCl2 (aq) 1 1