1. Types of chemical reactions – Part A
Dr. Chin Chu
River Dell Regional High School

2. Chemical changes (reactions)
2H2 + O2 2H2O
2NaOH(aq) + CuCl2(aq)  2NaCl(aq) + Cu(OH)2(s)
Cu + 2AgNO3  2Ag + Cu(NO3)2
NH3 + H2O  NH4OH
NH4NO3(s)  N2O(g) + 2H2O(g)
How could we get a handle on those changes?

3. Organization of chemical reactionsO C O C +
C + O2  CO2
Chemical reactions are merely rearrangements of atoms into different combinations called compounds.
There got to be some patterns that can be categorized into different types.

4. Unit objectives There are millions of reactions.
Can’t remember them all.
Fall into several categories.
Will learn 5 types.
Will be able to predict the products.
For some we will be able to predict whether they will happen at all.
Will recognize them by the reactants

5. Do you see the patterns? exercise
Balancing the following chemical equations:
aluminum(s) + iodine(s)  aluminum iodide(s)
sulfur trioxide + water  sulfuric acid (H2SO4)
lithium oxide + water  lithium hydroxide
Do you see the patterns?

6. Synthesis reactions Called also combination reactions
General Equation: A + B ® AB
Animation:
2 elements, or compounds combine to make one compound.
Mg +O2 ® MgO
SO2 + H2O ® H2SO3

7. Types of Synthesis Reactions
Combination of elements
Element + element ® compound
2Hg + O2 ® 2HgO
9Mg + 3N2 ® 3Mg3N2
Nonmetalic Oxides + water ® acid
SO2 + H2O ® H2SO3
P4O H2O ® 4H3PO4

8. Types of Synthesis reactions
Metalic oxides + water ® base
MgO + H2O ® Mg(OH)2
Na2O + H2O ® 2NaOH
Metallic oxides + nonmetallic oxide ® salt
MgO + CO2 ® MgCO3
CaO + SiO2 ® CaSiO3

9. Do you see the patterns? exercise
Watch the following video clips and write balanced equations:
1. Thermal decomposition of copper(II) nitrate
When heated, solid copper(II) nitrate decomposes into copper(II) oxide, nitrogen dioxide and water vapor.
2. Thermal decomposition of zinc carbonate
When heated, solid zinc carbonate decomposes into solid zinc oxide and carbon dioxide gas.
Do you see the patterns?

10. Decomposition reactions
Substances break apart.
General Form:
AB ® A + B
Animation:
Decomposition reactions are reverse of synthesis, with exceptions.

11. Decomposition reactions
Special Cases
Metal Chlorate ® metal chloride + oxygen
2KClO3 ®2KCl + 3O2
Metal bicarbonate ® metal oxide + carbon dioxide + water
2NaHCO3 ® Na2O + 2CO2 + H2O

12. Decomposition reactions
Special Cases
Most oxides are stable, only few decompose:
2HgO ® Hg + O2
Electrolysis of molten salt (decomposition by electricity) is the only means for decomposition for some substances:
2H2O ® 2H2 + O2
2NaCl ® 2Na + Cl2

13. Do you see the patterns? demos The methane bubble
The perfect combution (ethanol)
Burning of methanol
Do you see the patterns?

14. Combustion reactions
A compound composed of only C, H and maybe O is reacted with oxygen
If the combustion is complete, the products will be CO2 and H2O.
If the combustion is incomplete, the products will be CO and H2O.

15. exercises C4H10 + O2 ® (complete combustion)
C4H10 + O2 ® (incomplete combustion)
C6H12O6 + O2 ® (complete combustion)
C8H8 +O2 ® (incomplete combustion)

16. More exercises
Write a balanced equation for the complete combustion of each of these compounds.
a) acetic acid, HC2H3O2 c) glycerol, C3H8O3
b) decane, C10H22 d) sucrose, C12H22O11
Write a balanced equation for the incomplete combustion of each of these compounds.
a) glycerol, C3H8O c) acetic acid, HC2H3O2
b) glucose, C6H12O d) acetylene, C2H2