Determining if a compound is
soluble (aq) or NOT
• LOOK AT TABLE F
– LiOH
– Cu(NO3)2
– AgCl2
– MgS
– NaS2
– KOH
– aq
– aq
– insoluble = precipitate = s
– insoluble = precipitate = s
– aq
– aq
Double
Replacement
Reactions
Double Replacement
Format: AX + BY  AY + BX
DR rns occur in aqueous solutions
• So, what exactly happens to a substance
when we put it in water?
– depends if ionic or covalent
Dissolving
Covalent substance –
ex: sugar (C6H12O6)
C6H12O6(s)
 C6H12O6(aq)
• sugar molecules
spread out among
water molecules
Dissolving
• Ionic substance –
• ex: table salt (NaCl)
• NaCl(s) 
Na+1(aq) + Cl-1(aq)
•ions spread out
among water
molecules
Double Replacement Reactions
occur with 2 ionic compound
solutions
• Products can be:
- liquid (H2O)
- - gas
- - solid
Reactions
producing solids
Precipitation:
solid is formed opposite of
dissolving!
MOVIE
EX: Reactions producing Solids
2 NaOH(aq) + CuCl2(aq) 
2 NaCl(aq) + Cu(OH)2(s)
This is the Chemical Equation but it’s not
the whole story…
2 NaOH(aq) + CuCl2(aq)  2 NaCl(aq) + Cu(OH)2(s)
In solution it’s not NaOH and CuCl2
You actually have ions floating around
in water
Cu2+
Cu2+
Na+1
Na+1
Cu2+
Cl+1
Cu
Na+1
Cu2+
Cl+1
Cu
Cl-1
ions in solution are written as aqueous
• Reactants: 2Na+1(aq) + 2OH-1(aq) + Cu2+(aq) + 2Cl-1(aq)
• Products: 2Na+1(aq) + 2Cl-1(aq) + Cu(OH)2(s)
2 NaOH(aq) + CuCl2(aq)  2 NaCl(aq) + Cu(OH)2(s)
Net Ionic Equations
2Na+1(aq) + 2OH-1(aq) + Cu2+(aq) + 2Cl-1(aq)

2Na+1(aq) + 2Cl-1(aq) + Cu(OH)2(s)
•Notice some ions do not participate in reaction
• = spectator ions
• cross out spectator ions to get net ionic equation
Here’s what is really involved in the reaction…
2OH-1(aq) + Cu2+(aq)  Cu(OH)2(s)
Double Replacement Reactions
occur with 2 ionic compound
solutions
• Products can be:
- liquid (H2O)
- - gas
- - solid
Reactions that form Water
HBr(aq) + NaOH(aq)  H2O(l) + NaBr(aq)
H+1(aq) + Br-1(aq) + Na+1(aq) + OH-1(aq) 
H2O(l) + Na+1(aq) + Br-1(aq)
H+1(aq) + OH-1(aq)  H2O(l)
Reactions that form Gases
HCl(aq) + NaHCO3(aq)  H2CO3(aq) + NaCl(aq)
H2O(l) + CO2(g)
Reactions that form Gases
HCl(aq) + NaHCO3(aq) 
H2O(l) + CO2(g) + NaCl(aq)
H+1(aq) + Cl-1(aq) + Na+1(aq) + HCO3-1(aq) 
H2O(l) + CO2(g) + Na+1(aq) + Cl-1(aq)
H+1(aq) + HCO3-1(aq)  H2O(l) + CO2(g)
Conservation of Charge
total charge (reactant side)
must equal
total charge on product side
• 2OH-1(aq) + Cu2+(aq)  Cu(OH)2(s)
• -1 x 2
+
+2 = 0
• H+1(aq) + OH-1(aq)  H2O(l)
• H+1(aq) + HCO3-1(aq)  H2O(l) + CO2(g)