Review
TYPES OF CHEMICAL
REACTIONS
• What do you notice about the arrangement
of elements in the reactants and products?
• 2Al + Fe2O3 Æ 2Fe + Al2O3
• HCl + N
NaOH
OH Æ H2O + NaCl
N Cl
• Thousands of chemical reactions occur in
nature. Reactions can be classified into
one of several categories. Classification is
important for predicting products of
reactions.
– 1. SYNTHESIS REACTIONS
– 2. DECOMPOSITION REACTIONS
– 3. COMBUSTION
– 4. SINGLE REPLACEMENT REACTIONS
– 5. DOUBLE REPLACEMENT REACTIONS
SYNTHESIS
DECOMPOSITION
SINGLE
REPLACEMENT
DOUBLE
REPLACEMENT
COMBUSTION
2. DECOMPOSITION REACTIONS
1. SYNTHESIS REACTIONS
• Two or more substances combine to form
a new compound (composition or direct
combination).
• Examples:
• A + X → AX
• 2 Mg +O2 → 2 MgO
• 2 CO + O2 → 2 CO2 (car exhaust)
• CO2 + H2O Æ H2CO3 (carbonic acid)
Electrolysis of Water
• A single compound undergoes a reaction
that produces two or more simpler
substances (breakdown).
• Examples:
• AX → A + X
• 2 H2O2(l) → 2 H2O(l) +O2(g)
• 2 H2O(l) → 2 H2(g) +O2(g)
– Electrolysis- the decomposition of a
substance by applying an electric current.
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3. COMBUSTION REACTIONS
• A substance combines with oxygen (O2) to
release large amounts of energy in the
form of light and heat.
• CH4 +O2 → CO2 +2H2O
Writing Chemical Reactions
From Particle Diagrams
• Chemical formulas can be written from
diagrams as well
• Just like word problems, you must look at
your reactants and products as well as
balance the equation
http://www.chem.uiuc.edu/clcwebsite/meth.html
• Write the chemical reaction for the
following diagram:
Key:
= Atom of element X
= Atom of element C
Reactants
Products
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