1. Reactions in
Aqueous Solution

2. An Ionic Compound, CuCl2, in Water
CCR, page 177
An Ionic Compound, CuCl2, in Water

3. Aqueous Solutions
How do we know ions are present in aqueous solutions?
The solutions conduct electricity!
They are called ELECTROLYTES
HCl, CuCl2, and NaCl are strong electrolytes. They dissociate completely (or nearly so) into ions.

4. Aqueous Solutions CH3CO2H(aq) <---> CH3CO2-(aq) + H+(aq)
Acetic acid is a weak acid, it ionizes only to a small extent, so it is a weak electrolyte.
CH3CO2H(aq) <---> CH3CO2-(aq) + H+(aq)

5. Acids ---> H+ in water
HCl(aq) > H+(aq) + Cl-(aq)
Other strong acids include:
HI, HBr, HNO3, H2SO4, HClO4
Weak acids have H+ as the cation, and are not STRONG acids.
HCl is a strong acid

6. Base ---> OH- in water
BASES
Base ---> OH- in water
NaOH(aq) > Na+(aq) + OH-(aq)
Other strong bases include:
LiOH and KOH
Weak bases have OH- as the anion, and are not STRONG bases.
NaOH is a strong base

7. Ammonia, NH3 An Important Weak Base

8. Aqueous Solutions
Some compounds dissolve in water but do not conduct electricity. These are molecular compounds, made of molecules, so they do not split into charged particles. They are called nonelectrolytes.
Examples include:
sugar
ethanol
ethylene glycol

9. KISS Rules – Keep it Simple Solubility Rules
#1 – Soluble Cations: sodium, potassium, and ammonium are always soluble
#2 – Soluble Anions – nitrate, acetate, chlorate, perchlorate are always soluble
#3 – Soluble Anions – chloride, bromide, iodide are soluble EXCEPT with the SILVER GROUP – silver, mercury and lead
#4 – Soluble Anions – sulfate is soluble EXCEPT with the Silver Group or with strontium or barium
#5 – EVERYTHING ELSE IS INSOLUBLE

10. Net Ionic Equations Mg(s) + 2 HCl(aq) --> H2(g) + MgCl2(aq)
We really should write
Mg(s) H+(aq) Cl-(aq) >
H2(g) + Mg2+(aq) + 2 Cl-(aq)
The two Cl- ions are SPECTATOR IONS — they do not participate. Could have used NO3-.

11. We leave the spectator ions out —
Net Ionic Equations
Mg(s) HCl(aq) --> H2(g) + MgCl2(aq)
Mg(s) + 2 H+(aq) + 2 Cl-(aq)  H2(g) + Mg2+(aq) + 2 Cl-(aq)
We leave the spectator ions out —
Mg(s) H+(aq) ---> H2(g) + Mg2+(aq)
to give the NET IONIC EQUATION

12. Precipitation Reactions
The “driving force” is the formation of an insoluble compound — a precipitate.
Pb(NO3)2(aq) KI(aq)  2 KNO3(aq) + PbI2(s)
Net ionic equation
Pb2+(aq) I-(aq)  PbI2(s)