1. 4-3 General Types (Sections 7.6, 7.7)
And you

2. 1) Synthesis reaction
elements come together to form solid (in general but exceptions occur)
A + B → C or element + element → compound
Use periodic table to determine charges of elements.
Write product using criss-cross or balancing of charges to determine subscripts.
Balance equation

3. Synthesis rxn. Demo Al(s) + I2(s) →
Now balance this puppy please
2 Al(s) + 3 I2(s) → 2 AlI3(g)
You can see this is an example where a solid is not formed!!!
AlI3(g)

4. Synthesis Practice Na(s) + O2(g) → K(s) + S8(s) →
Now balance them please
Na2O(s)
K2S(S)

5. 2) Decomposition reaction
Solid heated to form solid and gas (in general)
C → A + B or
compound → element + element
Reactants will consist of just one compound.
Write compound’s elements as the products.
Remember the 7 diatomics!
Balance the equation

6. Decomposition Demo NI3(s) → http://www.youtube.com/watch?v=zU46hQ_xO0k
Now please balance this puppy
2 NI3(S)  N2(g) I2(g)
N2(g) + I2(g)

7. Decomposition practice
HgO(s) →
Now balance it please
2HgO (s)  2Hg (l) O2 (g)
H2O (l) → Products and balance please
2H2O (l)  2H2 (g) O2 (g)
Hg (l) O2 (g)

8. 3) Combustion reaction (my favorite)
CxHy (or CxHyOz) + O2 → CO2 + H2O
Rapid burning; one of the reactants will be O2.
For hydrocarbons (compounds with C, H, and/or O), the products are: CO2 + H2O

9. Combustion Demo CH4(g) + O2(g) →
The Methane Mamba! Demo
Balance please
CO2 (g) + H2O (g)

10. Combustion Practice
Recall the suggestion of starting with a 2 in front of the hydrocarbon, and reducing at the end if needed
C2H4O2 (l) + O2 (g) →
2 C2H4O2 (l) O2 (g) → 4 CO2 (g) + 4 H2O (g)
C2H4O2 (l) O2 (g) → 2 CO2 (g) + 2 H2O (g)

11. More combustion rxn. practice
C2H2(g) + O2(g) →
2 C2H2(g) + 5 O2(g) → 4 CO2 (g) H2O (g)
Starting with the 2 really helps on this one!

12. 4) Single Replacement rxn.
A + BC → AC + B or
element + compound → compound + element
Note: most take place in aqueous environment
Recall the H.S. dance parallel
Metals replace metals and nonmetals replace nonmetals.
Replacement occurs only if the element is higher on the activity list than the element in the compound.

13. Activity list or metalsK Ca Na Mg Al Zn Cr Fe Ni
Sn (tin)
Pb (lead) H Cu Hg
Ag (silver) Pt
Au (gold)
So Li would replace K if K was in a compound
Li is “more attractive” to that two-timing anion!!!
I hate that Li !!!!!!
Just kidding – don’t be a player hater

14. Activity list for non metals
fluorine
chlorine
bromine
Iodine
(general trend – but Cl may be more active)

15. Write the new compound with balanced charges and the individual element (is it diatomic?????).
If the element is lower on the list then the element in the compound, no reaction occurs.
Kind of a weird chemical hierarchy thing

16. Single replacement rxn. demo
Al(s) + CuCl2(aq) →
Demo in class
2 Al(s) + 3 CuCl2(aq) → 3 Cu (s) + 2 AlCl3 (aq)
Note Al is higher = “more attractive” than Cu

17. Single replacement practice
HCl(aq) + Zn(s) →
2 HCl(aq) + Zn(s) → ZnCl2 (aq) + H2 (g)
MgCl2(aq) + Zn(s) →
MgCl2(aq) + Zn(s) → No reaction !!!!!
Cl2(aq) + CaBr2(aq) →
Cl2(aq) + CaBr2(aq) → CaCl2 + Br2

18. 5) Double replacement AB(aq) + CD(aq) → AD + CB
compound + compound → compound + compound
Takes place in an aqueous environment
Metal pairs with nonmetal from other compound and vice versa.
Write new products with charges balancing.
Consult solubility chart to determine the insoluble compound (ppt). This chart, seen below, is also found on the inside back cover of your text and on page 170.

19. 1. Most nitrate (NO3-) salts are soluble.
2. Most salts of Na+, K+, and NH4+ are soluble.
3. Most chloride salts are soluble. Notable exceptions are AgCl, PbCl2, and Hg2Cl2.
4. Most sulfate salts are soluble. Notable exceptions are BaSO4, PbSO4, and CaSO4.
5. Most hydroxide (OH-) compounds are only slightly soluble. The important exceptions are NaOH and KOH. Ba(OH)2 and Ca(OH)2 are only moderately soluble.
6. Most sulfide (S-2), carbonate (CO3-2), and phosphate (PO4-3) salts are only slightly soluble.
Note: slightly soluble and moderately soluble are, essentially, the same as “insoluble”.

20. Posted on web page!!!!! (if you want your own copy)

21. Double replacement demo
CuCl2(aq) + Na2CO3(aq) →
CuCl2(aq) + Na2CO3(aq) → CuCO3(s) + 2NaCl(aq)
Note: see the solubility chart to know what forms if you do observe a ppt.

22. Practice double replacement rxns.
NaOH(aq) + FeCl3(aq) →
3NaOH(aq) + FeCl3(aq) → 3NaCl(aq) + Fe(OH)3
WOW that was FUN!!!!

23. Molecular, Complete Ionic, and Net Ionic Equations
The full double replacement is also called the” molecular equation.” For example, the molecular equation from above is:
3NaOH(aq) + FeCl3(aq) → 3NaCl(aq) + Fe(OH)3(s)

24. Molecular, Complete Ionic, and Net Ionic Equations
The full double replacement is also called the” molecular equation.” For example, the molecular equation from above is:
3NaOH(aq) + FeCl3(aq) → 3NaCl(aq) + Fe(OH)3(s)
A variation of this equation is the “complete ionic equation”, where the (aq) compounds are broken into their respective ions:
Like this:

25. 3NaOH(aq) + FeCl3(aq) → 3NaCl(aq) + Fe(OH)3(s)
3Na+(aq) + 3OH-(aq) + Fe+3(aq) + 3Cl-(aq) → 3Na+(aq) + 3Cl-(aq) + Fe(OH)3(s)
Note how the solid remains as a compound. This equation more accurately depicts what is happening in solution, since (aq) means that the ions a surrounded by water molecules (“hydrated”):

27. Cancel the redundant parts to find: 3OH-(aq) + Fe+3(aq) → Fe(OH)3(s)
A final version of the molecular equation is the “net ionic equation.” Simply put, this form only shows the ions that form the solid:
3Na+(aq) + 3OH-(aq) + Fe+3(aq) + 3Cl-(aq) → 3Na+(aq) + 3Cl-(aq) + Fe(OH)3(s)
Cancel the redundant parts to find:
3OH-(aq) + Fe+3(aq) → Fe(OH)3(s)

28. Practice: Na2SO4(aq) + BaCl2(aq) → Complete ionic: Net Ionic:
Note: All equations, regardless of the variation, require the atoms and charges to balance and the phases of matter included
Practice: Na2SO4(aq) + BaCl2(aq) →
Na2SO4(aq) + BaCl2(aq) → 2NaCl(aq) BaSO4(s)
Complete ionic:
2Na+ + SO4-2 + Ba+2 + 2Cl-  2Na+ + 2Cl- + Ba SO4 (s)
Net Ionic:
SO4-2(aq) + Ba+2(aq)  BaSO4 (S)
NOW that was FUN!!!!