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EQUATIONS
Coefficients1. The big numbers in front of the
compounds and/or elements in a
chemical reaction.
2. Represent the number of moles of that
compound or element in a chemical
reaction
3. Example:
2H2 + O2 2H2O
All represent coefficients. This reads 2 moles
of H2 reacts with 1 mole of O2 forms 2
moles of H2O
Subscripts1. Small numbers inside a chemical
formula
2. Represent the relative number of atoms in
a compound
3. Example:
Mg(NO3)2
All represent subcripts. This means that this
compound is made of 1 Mg and 2(NO3).
Each NO3 is made up of 1 N and 3 O
 Symbols
 + means reacts with when on the
reactant side and means and on the
product side
  means yields or produces
 Δ means heat is applied
TYPES OF CHEMICAL REACTIONS
Five Types of Chemical Reactions
1. Synthesis or direct combination
2. Decompostion or analysis
3. Single replacement
4. Double replacement
5. Combustion
SYNTHESIS OR DIRECT
COMBINATION
 Definition- A reaction in which two or
more substance form a compound
 Identification –Look at the product side
(right side) there will be only one product
 H2 O2 B2 I2 N2 Cl2 , all are elements.
 Examples:
 2H2 + O2  2H2O
 4Al + 3O2  2Al2O3
 Ca + Cl2  CaCl2
DECOMPOSITION OR
ANALYSIS
 Definition- A reaction in which a
compound is broken down.
 Identification- Look at the reactants (left
side) there will be one compound.
 Examples:
 2HgO  2Hg + O2
 2H2O  2H2 + O2
 2KClO3  2KCl + 3O2
SINGLE REPLACEMENT
 Definition- A reaction in which one
element reacts with one compound to
form another element and another
compound
 Identification- Look at the reactants (left
side) there will be one element and one
compound Remember the diatomics, H2
O2 B2 I2 N2 Cl2 , all are elements
 Examples:
 Zn + Cu(NO3)2  Cu + Zn(NO3)2
 Cu + 2 AgNO3  2Ag + Cu(NO3)2
 Mg + 2HCl  H2 + MgCl2
DOUBLE REPLACEMENT
 Definition- When two compounds react
and form two other compounds
 Identification- Look at the reactants (left
side) there will be two compounds.
 Examples:
 NaOH + HCl  NaCl + HOH
 AgNO3 + NaCl  AgCl + NaNO3
 3CaBr2 + 2Na3P  Ca3P2 + 6NaBr
COMBUSTION
 Definition- A reaction in which an
organic compound is burned and the
products are always carbon dioxide and
water
 Organic compound- a compound
composed of carbon and Hydrogen
 Identification- Look at the reactants and
look for O2 also the products will be CO2
and H2O
 Examples
 CH4 + O2  CO2 + 2H2O
 C3H8 + 5O2 3CO2 + 4H2O
BALANCING EQUATIONS



Equations are balanced to obey the
Law of Conservation of Mass.
To balance an equation coefficients are
added so that the number of atoms on
each side is constant
YOU CAN NEVER CHANGE
SUBSCRIPTS TO BALANCE.
REACTION STOICHIOMETRY-REVISTED
Steps for mole-mole problems
a. Copy the balanced equation(we will use
this as a “work area”
b. Place the given number of moles above
that compound in the balanced equation.
c. Place an X above the unknown substance
in the balanced equation
d. Set up and solve a mole-coefficient ratio
 Example:
 Hydrogen and oxygen react to produce
water according to the following equation:
 2H2 + O2  2H2O. How many moles of
oxygen gas needs to be reacted to produce
 7.5 moles of water?

 2H2 + O2  2H2O
 Answer:3.75 moles of O2