1. Reactions in Aqueous Solutions
Chapter 7

2. Basic Types of Equations
(Review of yesterday’s notes)

3. Synthesis element + element  compound A+XAX aluminum + oxygen  ?
analogy=?

4. Decomposition
compound  element + element
AXA+X
water?
analogy=?

5. Single Replacement compound and element element and compound
AX+BA+BX
chromium nitrate + copper ?
analogy=?

6. Double Replacement compound and compound  compound and compound
AX+BYAY+BX
Silver carbonate + magnesium phosphate?
analogy=?

7. What type of reaction begins with one compound?

8. Decomposition

9. What type of reaction begins with one compound and one element?

10. Single Replacement

11. What type of reaction begins with two elements?

12. Composition or Synthesis

13. What type of reaction begins with two compounds?

14. Double Displacement

15. Advanced Types

16. Types of Reactions I. Precipitation reactions
When aqueous solutions of ionic compounds are poured together a solid forms.
A solid that forms from mixed solutions is a precipitate.
If you’re not a part of the solution, your part of the precipitate.

17. Precipitation reactions
3NaOH(aq) + FeCl3(aq)3NaCl(aq) + Fe(OH)3(s)
is really
3Na+(aq)+3OH-(aq) + Fe+3(aq) + 3Cl-(aq)  Na+ (aq) + 3Cl- (aq) + Fe(OH)3(s)
So all that really happens is
3OH-(aq) + Fe+3(aq)  Fe(OH)3(s)
Double replacement reaction

18. Precipitation reaction
We can predict the products
Can only be certain by experimenting
The anion and cation switch partners
AgNO3(aq) + KCl(aq)?

19. Precipitations Reactions
Only happen if one of the products is insoluble
Otherwise all the ions stay in solution- nothing has happened.

20. Solubility Rules (p170) All nitrates are soluble
Alkali metals ions and NH4+ ions are soluble
Halides are soluble except Ag+, Pb+2, and Hg2+2
Most sulfates are soluble, except Pb+2, Ba+2, Hg+2,and Ca+2

21. Solubility Rules
Most hydroxides are slightly soluble (insoluble) except NaOH and KOH
Sulfides, carbonates, chromates, and phosphates are insoluble

22. Three Types of Equations
1) Molecular Equation- written as whole formulas, not the ions.
K2CrO4(aq) + Ba(NO3)2(aq)2KNO3(aq)+BaCrO4(s)
2) Complete Ionic equation show dissolved electrolytes as the ions.
2K+(aq) + CrO4-2(aq) + Ba+2(aq) + 2 NO3-(aq) 
BaCrO4(s) + 2K+ (aq) + 2 NO3- (aq)
Spectator ions are those that don’t react.

23. Three Type of Equations
3) Net Ionic equations show only those ions that react, not the spectator ions
Ba+2 (aq) + CrO4-2 (aq)  BaCrO4(s)
Write the three types of equations for the reactions when these solutions are mixed.
iron (III) sulfate and potassium sulfide

24. Answer iron (III) sulfate and potassium sulfide Molecular
Fe2(SO4)3 (aq) + 3K2S (aq) Fe2S3 (s) + 3K2SO4 (aq)
In your book, rule 2 trumps rule 6.
Ionic
2Fe+3 (aq) + 3SO4-2 (aq) + 6K+1 (aq) + 3S-2 (aq)
Fe2S3 (s) + 6K+1 (aq) + 3SO4-2 (aq)
Net Ionic
2Fe+3 (aq) + 3S-2 (aq) Fe2S3 (s)

25. Types of Reactions II. Acid-Base Acid + Base salt + water
H+ + OH- H2O (often called a neutralization reaction).
For our purposes an acid is a proton donor.
A base is a proton acceptor usually OH-
What is the net ionic equation for the reaction of HCl(aq) and KOH(aq)?

26. Types of Reaction III. Oxidation-Reduction called Redox
Ionic compounds are formed through the transfer of electrons.
An Oxidation-reduction reaction involves the transfer of electrons.
We need a way of keeping track.

27. Oxidation States A way of keeping track of the electrons.
Not necessarily true of what is in nature, but it works.
Need the rules for assigning (memorize).
The oxidation state of elements in their standard states is zero.
Oxidation state for monoatomic ions are the same as their charge.

28. Oxidation states
Oxide is assigned an oxidation state of -2 in its covalent compounds except as a peroxide.
In compounds with nonmetals hydrogen is assigned the oxidation state +1.
In its compounds fluoride is always –1.
6 The sum of the oxidation states must be zero in compounds or equal the charge of the ion.

29. Oxidation States
Assign the oxidation states to each element in the following.
CO2
NO3-
H2SO4
Fe2O3
Fe3O4

30. Oxidation States Assign the oxidation states to each element in the following.
+4 -2
CO2
NO3 -
H2SO4
Fe2O3
Fe3O4 is actually Fe+3Fe+3Fe+2

31. Transfer of electrons Oxidation-loss of electrons
Reduction-gain of electrons
Oxidation/reduction reaction-metal/nonmetal reaction (sometimes nonmetals undergo ox/red if oxygen is a reactant)
2Na(s)+Cl2(g)2NaCl(s)
Na + Cl Na++ Cl-
oxidation reduction

32. Oxidation-Reduction
Transfer electrons, so the oxidation states change.
Na + 2Cl2  2NaCl
CH4 + 2O2  CO2+ 2H2O
Oxidation is the loss of electrons.
Reduction is the gain of electrons.
OIL RIG
LEO GER

33. Oxidation-Reduction
Oxidation means an increase in oxidation state - lose electrons.
Reduction means a decrease in oxidation state - gain electrons.
The substance that is oxidized is called the reducing agent.
The substance that is reduced is called the oxidizing agent.

34. Identify the Oxidizing agent Reducing agent Substance oxidized
Substance reduced
Fe (s) + O2(g)  Fe2O3(s)
Fe2O3(s)+ 3 CO(g)  2 Fe(l) + 3 CO2(g)

35. Combustion
Reaction of a hydrocarbon/alcohol or other organic molecule with oxygen gas to produce carbon dioxide and water
C3H O2 → 3 CO HOH
CH3CH2OH O2 → 2 CO HOH