1. Review naming rules if you are rusty.
Ch 8 Problem set: p 290 #8, 10, 11, 15, 25, 26, 27, 35, 37
Good figures in the book to look at.... Hey, it’s January. Word on the street is that looking at illustrations, tables, & figures in the book is a good idea.
Review naming rules if you are rusty.

2. Chemical equations describe chemical reactions
8.1 Chemical Equations Chemical equations represent, with symbols and formulas, the reactants and products in a chemical reaction.
Chemical equations describe chemical reactions
Requirements for all chemical equations:
must show all reactants and products
formulas must be correct
Law of Conservation of Mass must be satisfied (equation must be balanced)
see reactants and products

3. 2NaCl(s)  2Na(s) + Cl2(g)
H Cl2  2 HCl
Hydrogen molecule reacts with Chlorine molecule to yield 2 molecules of Hydrochloric acid
Ex1:– decomposition of sodium chloride – start from scratch – use symbols, heat, etc.
2NaCl(s)  2Na(s) + Cl2(g)
Ex2: NaCl(s) = solid sodium chloride NaCl(aq) = solution of sodium chloride (in water)
H2O(l) - liquid water (not aqueous - redundant)

4. ppt or ↓ = precipitate (solid - only found on products side)
other symbols to know:
 = one way reactions
↔ = reversible reaction
(g) or ↑ = gas
ΔH = heat
cat = catalyst (a substance that speeds up a reaction without being used up in the reaction)
ppt or ↓ = precipitate (solid - only found on products side)
E:\student\ch08\sec01\vc05\hc608_01_v05fs.htm

5. So, what does the chemical equation actually mean?? H2 + Cl2  2 HCl
In atoms: 2 atoms of hydrogen gas react with 2 atoms of chlorine gas to yield 2 atoms of hydrogen and 2 atoms of chlorine
In molecules: 1 molecule of hydrogen gas reacts with 1 molecule of chlorine gas to produce 2 molecules of hydrochloric acid
In molar mass: H = 2.0; Cl = 71.0; HCl = 73.0
Video Clip

6. Balancing Chemical Equations A trial and error process
Balance 1 atom at a time
Balance atoms that appear only 1X per side first
Balance polyatomic ions as a whole unit
Balance diatomic elements last
Balance O and H last – if possible

7. Ex:
__2_Mg
____O2 + 
_2_MgO
Mg | Mg 1
O | O 1
If this doesn’t succeed, try doubling everything (particularly with combustion).
Balancing Equation Video
Try W.S. 8-1…

8. 8.2 Types of Chemical Reactions
There are 5 types of chemical reactions
Synthesis
Decomposition
Combustion
Single Replacement
Double Replacement
remember - first you’ve got to find the right products, then you gotta balance

9. 1. Synthesis (Combination)
Needs energy to occur (usually heat)
General Formula: A + B  AB Synthesis
Ba + S  Mg + Cl2 
Al + Cl2  Na + O2 
BaS
MgCl2
AlCl3
Na2O
2Al + 3Cl2  2AlCl3
4Na + O2  2Na2O

10. 2. Decomposition Needs energy to happen (heat or electricity)
General Formula: AB  A + B
Decomposition
FeCl3  HgO 
MgSO4 · 7H2O 
Fe + Cl2
Hg + O2
2FeCl3  2Fe + 3Cl2
2HgO  2Hg + O2
MgSO4 + 7H2O

11. 3. Combustion The reaction of hydrocarbons and oxygen General Formula:
Combustion Reaction
CxHy + O2  H2O + CO2
CH4 C3H8
C4H10 C2H5OH

12. 4. Single Replacement Takes place in aqueous solutions
Needs very little energy to happen
2 Types
Positive Ions Switch
General Formula: AB + M  MB + A
HI + Mg 
AlCl3 + Ca 
Ca + HOH  2
MgI2 + H2 3 2
3CaCl2 + 2Al 2
Ca(OH)2 + H2
Single Replacement Diagram

13. General Formula: AB + X  AX + B
- Negative Ions Switch
General Formula: AB + X  AX + B
NaCl + F2 
BaS + O2 
NaF + Cl2
BaO + S

14. 5. Double Replacement FeCl3 + NaOH  Double Replacement Picture
again - aqueous solution - little energy - usually forms one soluble ionic product (aka - aqueous) and either a ppt, water, or a gas that bubbles out of water
General Formula: AB + CD  CB + AD
FeCl3 + NaOH 
H2SO4 + NaOH 
NH4Cl + NaOH 
Double Replacement Picture

15. 8.3 Activity Series of the Elements
hey, some reactions happen and some don’t - for synthesis, combustion, and decomposition, we will assume they all happen given sufficient activation energy ( Ea )
For single replacement, use the Activity Series!
Ca + H2O yields Al + H2O yields
Al + HI yields Cu + HI yields
NaCl + F2  NaF + Cl2 →

16. Any single element above an element in a compound will replace it.
Rules for the single replacement activity series:
Any single element above an element in a compound will replace it.
The top 6 elements react with water.
Metals above H react with acids (molecules that start with H – not water).
The nonmetal reactivity series is F> Cl > Br...
Metal Reactivity Video

17. For double replacement reactions, use a Solubility Table!
Rules for double replacement reactions using a solubility table:
If one of the products formed is water, the reaction happens.
If a gas is formed, the reaction happens.
If an insoluble product forms (I or Ss), the reaction happens (actually a reaction may happen when two soluble products form, but it doesn’t go to completion and is not directly observable). **** refer to “ions in solution” lab

18. Na2CrO4 + KCl  NR (both products soluble)
examples from the lab -
Na2CrO4 + KCl  NR (both products soluble)
FeCl3 + KOH  Fe(OH)3(ppt) KCl(aq)
Yes! The reaction happens!
Note: precipitate symbols include (ppt), (s), and .
HCl + NaOH 

19. Heavier stuff doesn’t dissolve well
NIB Solubility Trends
Cations -very soluble - Na, K, ammonium
-very insoluble- Ag, Pb, Hg, transitions
Anions - very soluble - nitrate
for monatomics- F>Cl>Br ....
very insoluble - carbonate, hydroxide, phosphate, sulfate
sulfides - decompose
general trend - As size decreases, solubility increases OR
Heavier stuff doesn’t dissolve well

20. Showing Energy Changes in Equations
Endothermic – put in heat (left side of equation)
A + B + heat  C ΔH is positive
Exothermic – releases heat (right side)
- A + B  C + heat ΔH is negative

21. Some helpful notes on writing phases in chemical reactions
Metals are solids (except Hg)
In SR and DR reactions reactants that are compounds are always aqueous
In SR and DR reactions products that are compounds should have their phases identified using a solubility chart (aq. vs. ppt)
In S and D reactions ionic compounds are always solid
In C reactions, the water, CO2, and O2 are gases. The hydrocarbon is a gas but usually becomes a liquid at C=6 or higher
Most other covalent compounds are gases
Acids (chemicals starting with H) are aqueous