1. Reactions in Aqueous Solutions

2. Reactions
When you mix 2 aqueous ionic compounds, there are 2 possible outcomes:
1) compounds will remain in solution without reacting
AB + CD  NR
(no reaction)
2) you can have a double displacement reaction (DD)
WX + YZ  WZ + YX

3. Evidence? How do you recognize if DD has occurred?
precipitate (ppt) forms
gas forms
water forms

4. A. Formation of a Precipitate
ions are removed by the formation of an insoluble solid
need to use solubility guidelines
Examples:
1) Pb(NO3)2(aq) +2NaI(aq)  2NaNO3(aq) + PbI2(s)
a) see solubility guidelines:
NaNO3 is soluble and PbI2 is insoluble

5. A. Formation of a Precipitate
Examples:
2) The reaction of:
potassium carbonate sol’n and copper (II) sulfate sol’n
see solubility guidelines to find if a product is insoluble
write word equation for the reaction
write balanced chemical equation
write total ionic equation (TIE)
write net ionic equation (NIE) to show reacting ions only
identify the reacting ions
identify the spectator ions (the ions that remain on each side of the eq’n)

6. A. Formation of a Precipitate
Examples:
3) NaNO3(aq) + CuSO4(aq)  ?
see solubility guidelines to find if a product is insoluble

7. B. Formation of a Gas
ions are removed from the solution in the form of a gaseous product
gases are commonly H2(g), H2S(g), SO2(g), CO2(g), and NH3(g).
often the result of molecular compounds (nonmetal-nonmetal) involved in the rxn

8. B. Formation of a Gas Na2SO3(aq) + 2HCl(aq)  2NaCl(aq) + H2SO3(aq)
Examples:
1) hydrogen gas
LiH(s) + H2O(l)  LiOH(aq) + H2(g)
2) sulfur dioxide gas
Na2SO3(aq) HCl(aq)  2NaCl(aq) + H2SO3(aq)
H2SO3(aq)  SO2(g) + H2O(l)
Net rxn:
Na2SO3(aq) + 2HCl(aq)  2NaCl(aq) + SO2(g) + H2O(l)
3) For other gases, see p340

9. C. Formation of Water
H+ and OH- ions are removed from solution as water
also called neutralization reaction between acid and base
forms water and a salt

10. C. Formation of Water Examples HCl(aq) + KOH(aq) 
H2SO4(aq) + NaOH(aq) 
HNO3(aq) + MgO(s) 
LiOH(s) CO2(g) 

11. C. Formation of Water Examples HCl(aq) + KOH(aq)  KCl(aq) + H2O(l)
H2SO4(aq) +2 NaOH(aq)  K2SO4(aq) + 2H2O(l)
2 HNO3(aq) + MgO(s)  Mg(NO3)2(aq) + H2O(l)
2 LiOH(s) + CO2(g)  Li2CO3 (aq) + H2O(l)
NOTE: NIE is always the same for neutralization reaction (rxn #1 and #2)!