Chapter 5 - Chapter
5
...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Chapter
5
 Chemical
Reactions
and
Equations
 I. Chemical
Reaction:
the
conversion
of
one
substance
or
set
of
substances
into
another.
 1. Reactant:
substance
that
we
start.
 2. Product:
new
substance
that
forms
during
the
reaction.
 Example:
NaOH(aq)+
HCl(aq)=
NaCl(aq)+
H2O(l)
 
 NaOH,
HCl
:
reactants.
 
 NaCl,
H20
:
products.
 II. The
clues
most
often
when
a
chemical
reaction
occurs:
 1. Change
in
color.
 2. Production
of
light.
 3. Formation
of
a
solid
(precipitate
in
solution,
smoke
in
air,
or
a
metal
coating).
 4. Formation
of
a
gas
(bubbles
in
solution
of
fumes
in
the
gaseous
state).
 5. Absorption
or
release
of
heat
(
sometimes
appearing
as
a
flame).
 III. Chemical
Equation:
 1. Chemical
equation:
a
symbolic
representation
of
a
chemical
reaction.
 Ex:
aluminum
+
iron(III)
oxide
+
heat
aluminum
oxide
+
iron
 
 Al(s)
+
Fe2O3a
+
heat

Al2O3(s)
+
Fe(l)
 It
is
important
to
remember
that
you
cannot
change
the
subscript
of
an
element
in
a
 compound
to
balance
an
equation.
For
example,
Al2O3
cannot
be
change
to
AlO3
to
 balance
the
number
of
aluminum
atoms.
 2. Balancing
chemical
equations:
 • When
the
atoms
of
the
reactants
and
products
have
not
yet
been
equalized,
the
 equation
is
called
a
skeletal
equation
or
unbalanced
equation.
 • To
balance
equations:
the
total
number
of
each
element
on
the
reactant’s
side
 must
equal
the
product’s
side.
The
subscripts
correspond
to
the
element
before
 it.
The
coefficient
corresponds
to
all
the
elements
after
it.
 Ex:
5H2O
there
are
five
H20
molecules,
and
each
H2O
molecule
has
two
hydrogen
 atoms
and
one
oxygen
atom.
Therefore,
there
ten
total
hydrogen
and
five
 oxygen
atoms.
 IV. Predicting
Chemical
Reactions:
 1. Decomposition
reactions:
it
breaks
down
into
the
elements
of
which
it
is
composed
or
 into
simpler
compounds.
CD

C
+
D
 Reactants:
1
compound
 Products:
2
elements
(or
small
compounds)
 Decomposition
reactions
that
occur
when
compound
are
heated.
(
for
more
information
 see
table
5.2
page
168)
 2. Combination
reactions:
A
+
B

AB
 Reactants:
2
elements
or
compounds
 Products:
1
compound
 
 • Most
metals
react
with
most
nonmetals
to
form
ionic
compounds.
The
products
 can
be
predicts
from
the
charges
expected
for
the
cation
of
the
metal
and
the
 anion
of
the
nonmetal.
Ex:
2Al(s)
+
3Br(l)
2AlBr3(s)
 • A
nonmetal
may
react
with
a
more
reactive
nonmetal
to
form
a
molecular
 compound.
Ex:
8S(s)
+
8O2(g)

8SO2(g)
 • A
compound
and
an
element
may
combine
to
form
another
compound
if
one
 exists
with
a
higher
atom:
atom
ratio.
Ex:
2C(s)
+
O2(g)
2CO(g).

 2CO(g)
+
O2(g)

2CO2(g).
 • Two
compounds
may
react
to
form
a
new
compound.
Ex:
CaO(s)
+
CO2(g)

 CaCO3(s)
 3. Single‐Displacement
Reactions:
A
+
CD

C
+
AD
 Reactants:
1
element
and
1
compound
 Products:
1
element
and
1
compound
 More
active
element
displaces
a
less
active
element
form
its
compounds
(
see
 activity
series
on
page
173)
 4. Double‐Displacement
Reactions:
CD
+
EF

CF
+
ED
 Reactants:
2
compounds
 Products:
2
compounds
 Double‐
displacement
reactions
occur
when
there
is
one
of
three
clues:
 precipitation,
gas
formation,
and
acid‐base
neutralization
reactions.
 • Precipitation:
an
insoluble
ionic
compound
that
does
not
dissolve
in
water
(
see
 table
5.3:
Rules
Used
to
Predict
the
Solubility
of
Ionic
Compounds)
 Ex:
BaCl2(aq)
+
Na2SO4(aq)

BaSO4(s)
+
NaCl(aq)
 • Gas
formation
reactions:
the
formation
of
an
insoluble
(
or
only
slightly
soluble)
 gas
provides
the
driving
force
for
a
reaction.
 Ex:
Zn(s)
+
HCl(aq)

ZnCl2(aq)
+
H2(g)
 • Acid‐base
Neutralization
Reactions:
an
acid
reacts
with
a
base
to
form
an
ionic
 compound
and
water.
 Ex:
HCl(aq)
+
NaOH(aq)

NaCl(aq)
+
H2O(l)
 5. Combustion
reactions:
any
reaction
that
involves
oxygen
molecules
as
a
reactant
and
 that
rapidly
produces
heat
and
flame
is
a
combustion
reaction.
 Ex:
CH4(g)
+
2O2(g)

CO2(g)
+
2H2O(g)
 V. Representing
reactions
in
aqueous
solution:
 1. Molecular
equation:
represent
the
substances
as
if
they
existed
as
molecules
in
solution.
 Ex:
AgNO3(aq)
+
KBr(aq)
AgBr(s)
+
KNO3(aq)
 2. Ionic
equation:
dissociate
into
ions
in
solution
 Ex:
Ag+(aq)
+
NO3‐(aq)
+
K+(aq)
+
Br‐(aq)

AgBr(s)
+
K+(aq)
+
NO3‐(aq)
 






3.



Spectator
ions:
it
can
be
eliminated
from
both
sides
 Ex:
Ag+(aq)
+
Br‐(aq)

AgBr(s)
 ...
View Full Document

This note was uploaded on 11/16/2009 for the course MATH 140a taught by Professor Staff during the Spring '08 term at UC Irvine.

Ask a homework question - tutors are online