Download Types of Reactions notes 02 Types of chemical reactions

Chemical
Equations
Chemical change involves a
reorganization of the atoms in one
or more substances.
Chemical Equation
A representation of a chemical reaction:
CH4 + O2  CO2 + H2O
reactants
products
Physical States
When you see a chemical formula, often the
formula is followed by a symbol in
parentheses. For example:
 H2O(l) - the water is liquid
 H2O(s) - the water is solid (ice)
 H2O(g)- the water is a gas (steam)
 NaCl(aq) – means that the chemical is
disolved in water. In this case it would be
salt dissolved in water.
The Magnificent 7
(diatomic molecules)
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Certain elements do not exist naturally as
a single atom. They exist in pairs.
So when writing out a chemical equation it
is important to write the chemical formula
to show that.
The 7 are: H2, N2, O2, F2, Cl2, Br2, and I2
Types of Reactions
Synthesis Reaction
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When two or more reactants come together to
make one product. Also called Combination.
Example:
N2 + H2  NH3
Note that diatomic molecules (Magnificent 7!)
must be diatomic in their elemental form.
Decomposition Reaction
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When a single compound is broken down
into two or more products
Example:
H2O  H2 + O2
Single Displacement Reaction
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When an element and an ionic compound
react and the element takes the place of
its comparable ion
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Metal element  takes positive ion’s place
Nonmetal element  takes negative ion’
place
Examples:
Mg + FeCl3  MgCl2 + Fe
Br2 + FeCl3  FeBr3 + Cl2
Mg + FeCl3  MgCl2 + Fe
Br2 + FeCl3  FeBr3 + Cl2
Notice!
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The neutral atom joins the compound becoming
a charged ion.
The products MUST be electronically neutral.
Since Mg becomes Mg+2, two Cl ions neutralize
it.
The charge on the transition metal stays the
same if it remains as an ion (iron is +3 charge in
both the reactant and product)
Double Displacement Reaction
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When two ionic compounds switch their partner
ions.
Positive goes with other negative and vice versa.
Switcheroo!
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Example:
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NaCl + MgBr2  MgCl2 + NaBr
Pb(NO3)2 + Na2SO4  NaNO3 + PbSO4
NaCl + MgBr2  MgCl2 + NaBr
Pb(NO3)2 + Na2SO4  NaNO3 + PbSO4
Notice!
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The reactants and products MUST be
electronically neutral
All ions keep their charge from reactants to
products
Do not get fooled into thinking that if there are a
certain number atoms of an element in the
reactants, there will be the same number in the
products!
Polyatomic ions are very common in these types
of reactions. Make sure you can spot them!
Combustion Reactions
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When a hydrocarbon (something with C’s
and H’s and sometimes O’s – organic
molecule) reacts with Oxygen to form
water and carbon dioxide and heat
energy. 
Example:
CH4 + O2  CO2 + H2O
C4H8 + O2  CO2 + H2O
Acid/Base reaction
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When an acid reacts with a base, water
forms
Acids produce H+ in water
Bases produce OH- in water
Example:
HNO3 + KOH  HOH (or H2O) + KNO3
What type of equation are each of
the following reactions?
P + O2  P2O5
C3H5O + O2  CO2 + H2O
NH4NO3  N2O + H2O
Fe2O3 + C  Fe + CO
CO2 + H2O  H2CO3
CuNO3 + Na2SO4  Cu2SO4 + NaNO3
Check Your Answers
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P + O2  P2O5
Synthesis
C3H5O + O2  CO2 + H2O
Combustion
NH4NO3  N2O + H2O
Decomposition
Fe2O3 + C  Fe + CO
Single
Displacement
Check Your Answers
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CO2 + H2O  H2CO3
Synthesis
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CuNO3 + Na2SO4  Cu2SO4 + NaNO3
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Double Displacement