Transcript Numbers, Symbols and Conventions used in chemistry

TYPES OF CHEMICAL
REACTIONS – PART A
Dr. Chin Chu
River Dell Regional High School
CHEMICAL CHANGES (REACTIONS)
ORGANIZATION OF CHEMICAL REACTIONS
C
+
O
O

O C
O
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.
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
EXERCISE
Balancing the following chemical equations:
1. aluminum(s) + iodine(s)  aluminum iodide(s)
2. sulfur trioxide + water  sulfuric acid (H2SO4)
3. lithium oxide + water  lithium hydroxide
Do you see the patterns?
SYNTHESIS REACTIONS

Called also combination reactions

General Equation: A + B 

Animation:
2 elements, or compounds combine to make one
compound.
 Mg +O2 MgO
 SO2 + H2O  H2SO3

TYPES OF SYNTHESIS REACTIONS
Combination of elements
Element + element  compound
 2Hg + O2  2HgO
 9Mg + 3N2  3Mg3N2
Nonmetalic Oxides + water  acid
 SO2 + H2O  H2SO3
 P4O10 + 6H2O  4H3PO4
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
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?
DECOMPOSITION REACTIONS
Substances break apart.

General Form:
AB  A + B


Animation:
Decomposition reactions are reverse of
synthesis, with exceptions.
DECOMPOSITION REACTIONS
Special Cases

Metal Chlorate  metal chloride + oxygen
2KClO3 2KCl + 3O2

Metal bicarbonate  metal oxide + carbon dioxide
+ water
2NaHCO3  Na2O + 2CO2 + H2O
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
DEMOS
1. The methane bubble
2. The perfect combution (ethanol)
http://www.youtube.com/watch?v=Lb-KB_BshUc&NR=1
3. Burning of methanol
Do you see the patterns?
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.
EXERCISES
 C4H10
+ O2  (complete combustion)
 C4H10
+ O2  (incomplete combustion)
 C6H12O6
 C8H8
+ O2  (complete combustion)
+O2  (incomplete combustion)
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, C3H8O3
c) acetic acid, HC2H3O2
b) glucose, C6H12O6
d) acetylene, C2H2