1. The Driving Forces of CHEMICAL REACTIONS

2. Precipitation Reactions
EXCHANGE:
Precipitation Reactions
REACTIONS

3. IONIC COMPOUNDS Compounds in Aqueous Solution
Most redox reactions are in water — aqueous solutions - and involve ionic compounds
K+(aq) + MnO4-(aq)
KMnO4 in water
To play the movies and simulations included, view the presentation in Slide Show Mode.

4. Insoluble products: Precipitation formation

5. Precipitation Reactions
The “driving force”= solid.
Pb(NO3)2(aq) KI(aq) g
2 KNO3(aq) PbI2(s)
Net ionic equation
Pb2+(aq) I-(aq) g PbI2(s)

6. Water Solubility of Ionic Compounds
If one ion from the “Soluble Compound” list is present, the compound is water soluble.

7. Aqueous Solutions
Solutions that conduct electricity
are called ELECTROLYTES
Strong electrolytes dissociate completely (or nearly so) into ions.

8. Aqueous Solutions CH3CO2H(aq) ---> CH3CO2-(aq) + H+(aq)
Acids that ionize only to a small extent are called weak electrolyte.
CH3CO2H(aq) ---> CH3CO2-(aq) + H+(aq)

9. Aqueous Solutions
Some compounds dissolve in water but do not conduct electricity. They are called nonelectrolytes.
Examples include:
sugar
ethanol
ethylene glycol

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

12. EXCHANGE
Acid-Base
Reactions
REACTIONS

13. Acid-Base Reactions The “driving force” = water. Net ionic equation
OH-(aq) + H+(aq) g H2O(l)
This applies to ALL reactions of STRONG acids and bases.

14. Know the strong acids & bases!

15. ACIDS Some strong acids are HCl hydrochloric H2SO4 sulfuric
An acid g H+ in water
Some strong acids are
HCl hydrochloric
H2SO4 sulfuric
HClO4 perchloric
HNO3 nitric
HNO3

16. BASES Base g OH- in water NaOH(aq) ---> Na+(aq) + OH-(aq)
NaOH is a strong base

17. CaO(s) + H2O(liq) g Ca(OH)2(aq) Indicator shows solution is basic.
BASES
CaO(s) + H2O(liq) g Ca(OH)2(aq)
Metal oxides are bases
CaO in water.
Indicator shows solution is basic.

18. ACIDS CO2(aq) + H2O(l) g H2CO3(aq) SO3(aq) + H2O(l) g H2SO4(aq)
Nonmetal oxides can be acids
CO2(aq) + H2O(l) g H2CO3(aq)
SO3(aq) + H2O(l) g H2SO4(aq)
and can come from burning coal and oil.

19. EXCHANGE
Gas-Forming
Reactions
REACTIONS

21. Gas Forming Reactions

22. Electrochemical Reactions
REDOX REACTIONS
REACTIONS

23. Why Study Redox Reactions
Batteries
Corrosion
Manufacturing metals
Fuels

24. Examples of Redox Reactions
Combustion
Fuel + Oxygen
Metal (Mg) + Oxygen

25. Examples of Redox Reactions
Synthesis
Metal + halogen
2 Al + 3 Br2 ---> 2AlBr3

26. REDOX REACTIONS
Redox reactions are characterized by ELECTRON TRANSFER between an electron donor and electron acceptor.

27. Lose electrons: OXIDATION Gain electrons: REDUCTION
LEO says GER
Lose electrons: OXIDATION
Gain electrons: REDUCTION

28. REDOX REACTIONS
Single replacement
Cu(s) + 2 Ag+ (aq) gCu2+ (aq) + 2 Ag(s)
In all reactions; if something is oxidized then something needs to be reduced

29. Elemental Oxygen always REDUCED (GAIN)
Combustion
Fuel + Oxygen
Metal (Mg) + Oxygen

30. Elemental Metals Always OXIDIZED (LOSE)
Cu + HNO3
Cu = oxidized
HNO3 = reduced
Mg + HCl
Mg = oxidized
H+ = reduced

31. OXIDATION NUMBERS
The electric charge an element APPEARS to have when electrons are counted by some arbitrary rules:

33. Recognizing a Redox Reaction
OXIDATION NUMBERS = CHARGE
2 Al(s) + 3 Cu2+(aq) --> 2 Al3+(aq) + 3 Cu(s)
Al(s) --> Al3+(aq) + 3 e-
Therefore, Al is OXIDIZED
Ox. no. of Al increases as e- are donated by the metal.

34. Recognizing a Redox Reaction
OXIDATION NUMBERS = CHARGE
2 Al(s) + 3 Cu2+(aq) --> 2 Al3+(aq) + 3 Cu(s)
Cu2+(aq) + 2 e- --> Cu(s)
Therefore, Cu is REDUCED
Ox. no. of Cu decreases as e- are accepted by the ion.

35. REDOX REACTIONS EXCHANGE: Precipitation Reactions EXCHANGE Gas-Forming
Acid-Base
Reactions
REACTIONS
REDOX REACTIONS