Chapter 8: Chemical Reactions
OBJECTIVES
1. Identify when a chemical reaction occurs
2. Write chemical equations
3. Balance chemical equations
4. Predict the products of reactions when the
reactants are known
5. Use the Activity series to determine if a
reaction will occur
A. Energy and Chemical Reactions
_____________
EXOTHERMIC
Releases Energy such
as heat, sound, and
light. Feels Hot.
ENDOTHERMIC
_____________
Absorbs Energy such
as heat; feels cold.
A. Energy and Chemical Reactions
ACTIVATION ENERGY
Energy needed to trigger
a reaction.
EXO
ENDO
B. Indications of chemical reactions
 Evolution of heat and light
 Burning Alcohol
 Formation of a gas
 NaOCl + HCl  NaCl + H20 + Cl2
 Formation of a precipitate
 CuSO4 + NaOH  Cu(OH)2 + Na2SO4
 Color change
 HNO3 + Cu  Cu(NO3)2 + NO2 + H2O
C. Chemical Equations
Right side are
PRODUCTS
Left side are
REACTANTS
PbCl2
+
Na2CrO4

PbCrO4
Yields
Number of moles
or particles
+
2NaCl
C. Chemical Equations
THE MAGNIFICENT SEVEN
These elements exist in nature as diatomic
molecules, never as a lone atom.
H2, N2, O2 F2, Cl2, Br2, I2
And Hydrogen!
C. Chemical Equations - Symbols






(s) or ↓as in NaCl (s)
(l) as in H2O (l)
(g) as in H2O (g)
(aq) as in NaCl (aq)

75o C
 or 
Pd

Yields
Reversible reaction
Solid or precipitate
Liquid
gas
Aqueous i.e. dissolved in water
Heat added
Catalyst used
D. Balancing Equations
During a process called electrolysis (electric current)
water is converted to hydrogen gas and oxygen gas.
NEVER EVER CHANGE A SUBSCRIPT


2 H2O
2 H2
4 2 H 2 4
2 1
O
2
+
O2
D. Balancing Equations
Fe2O3
Treat Polyatomic ions as one unit
+ 3 H2SO4
Fe2(SO4)3 + 3H2O
2 Fe
2
3 O
1 3
6 2 H
2 6
3 1 SO4 3
E. Types of reactions
1. Synthesis Reactions
General Form: A + B  AB
Definition: Two substances forming a new compound
Mg
Fe
+
+
O2 
O2 
Assuming Fe+4
Assuming Fe+3
Fe
+
O2 
E. Types of reactions
2. Decomposition Reactions
General Form: AB  A + B
Definition: A compound breaks down into 2 or more
H2O
HgO
𝐸𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑖𝑡𝑦
Δ
Metal hydroxides 
Metal oxides and
water
Ca(OH)2 
Al2(CO3)3 
Metal carbonates 
Metal oxides and CO2
E. Types of reactions
3. Single Replacement Reactions
General Form: A + BC  B + AC OR Y + AX  X + AY
Definition: A metal or halogen switches with another
Al + Pb(NO3)2
Na + H2O 
F2+
HCl 

E. Types of reactions
4. Double Replacement Reactions
General Form: AX + BY  BX + AY
Definition: Two metals swap positions
KI
FeS
+
+
Pb(NO3)2
HCl


E. Types of reactions
5. Acid Base Reactions (Really a Double replacement)
General Form: HX + BOH  BX + H2O
Definition: Double replacement that makes water
Acids start with H
Bases end with OH
HCl
+
NaOH 
E. Types of reactions
6. Combustion Reactions
General Form: CxHyOz + O2  CO2 + H2O
Definition: Hydrocarbon burns making CO2 and H2O
CO2 and H2O are
ALWAYS
the products
O2 indicates
combustion
C3H6O2
C8H18
+
+
O2
O2


F. Factors that influence Reaction rate
Reaction rate is determined by particle collisions
Successful collisions:
Collide with each other
Have the correct orientation
Have enough kinetic energy to break bonds
Na Cl
Na Cl K
K
F. Factors that influence Reaction rate
K
Na Cl
F. Factors that influence Reaction rate
Four major influences:
 Temperature
Increase speeds up reactions
Faster particles (more KE)
 Concentration
Higher concentration speeds up reactions
More chances to collide
 Surface area
Higher SA speeds up reactions
More chances to collide
 Catalyst
F. Iodine Clock Reaction
G. Activity Series
Most Reactive
Li
Rb
K
React with cold water and acids,
replacing hydrogen. React with
oxygen forming oxides.
F2
Cl2
Ba
Br2
Sr
I2
Ca
Na
Mg
Al
Mn
Zn
React with STEAM and acids
replacing hydrogen. React with
oxygen forming oxides.
Cr
Fe
Cd
Co
Ni
Sn
Pb
H2
Sb
Bi
Do NOT react with water. React
with acids replacing hydrogen.
React with oxygen forming
oxides.
React with oxygen forming
oxides.
Cu
Hg
Least Reactive
TABLE OF HALOGENS
Ag
Pt
Au
Fairly unreactive.
H. Solubility Chart