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Chapter 11
Chemical Reactions
Chapter 11 Section 1
Describing chemical reactions
Chemical equations
►A
chemical reaction is one or more
substances changing to one or more new
substances
► The starting substances are called reactants
► The ending substances are called products
► Reactants  Products
Writing Equations
► Any
chemical reaction will have the
reactants to the left of the arrow separated
by plus signs and the products to the right
of the arrow separated by plus signs.
► Word equation- elements or compounds are
represented by words
 Example – Iron + oxygen  Iron(III)oxide
Chemical equation
► Written
the same way, but elements and
compounds are represented by symbols and
formulas.
 Example – Fe + O2  Fe2O3
► Skeleton
equation- does not include the
relative amounts of the reactants and
products.
Catalyst
► Speeds
up a chemical reaction but is not
used up in the reaction.
► Catalysts are neither reactants or products.
► The formula for the catalyst may be written
above the arrow in a chemical equation.
Balancing equations
► In
a chemical equation, each side of the
equation must have the same number of
atoms of each element.
► Equations are balanced by placing
coefficients to the left of the formulas.
 Example  Balanced
Fe + O2  Fe2O3 Not balanced
4Fe + 3O2  2Fe2O3
Chapter 11 Section 2
Types of Chemical Reactions
Classifying Reactions
► There





are five general types of reactions
Combination
Decomposition
Single replacement
Double replacement
Combustion
Combination reactions
► Two
or more substances react to form one
new substance.
► A + B  AB
► The final product will always be a single
compound.
Decomposition Reaction
►A
single compound breaks down into two or
more simpler products.
► AB A + B
► Decomposition reactions will always start
with a single reactant. Most require energy.
► These are the opposite of combination
reactions.
Single replacement reaction
► One
element replaces a second element in a
compound.
► A +BC  AC + B
► Both the reactants and the products will
contain one element and one compound.
► A metal can only be replaced by a metal
that is more reactive than the original.
Double replacement reaction
► An
exchange of positive ions between two
compounds.
► AB + CD  CB + AD
► These reactions often take place in aqueous
solutions (dissolved in water).
Combustion Reaction
► An
element or compound reacts with
oxygen producing energy.
► CH4 + O2  CO2 + H2O
► Mg + O2  MgO
Predicting Reactions
► Combustion
contain O2 in reactants.
► Combination combines two to form one
► Decomposition breaks one into two
► Single replacement has one compound and
one element on both sides of the equation.
► Double replacement involves two
compounds on both sides of the equation.
Chapter 11 Section 3
Reactions in Aqueous Solution
Net Ionic Equations
► Complete
ionic equation- an equation that
shows dissolved ionic compounds as
dissociated free ions.
► Net Ionic- an equation for a reaction in
solution that shows only those particles that
are directly involved in the chemical change.
► Spectator ion- An ion that appears on both
sides of an equation and is not directly
involved in the reaction.
Complete ionic equation
► Aqueous
silver chloride reacts with aqueous
sodium bromide to produce aqueous silver
bromide and solid sodium chloride.
► Chemical equation► AgCl(aq) + NaBr(aq)  AgBr(aq)+ NaCl(s)
► Complete ionic equation
►
Ag+ + Cl- + Na+ + Br-  Ag+
► Net
ionic equation
► Na+(aq) +
Cl-(aq)  NaCl(s)
+
Br- + NaCl(s)