Ch' 8 Notes Chemical Reactions

1
Ch. 8 Notes -- Chemical Reactions

• Chemical equations give information in two major
  areas
• 1. _____________ and ______________ of the
  reaction.
• 2. Coefficients of a balanced chemical equation
  tell us the ______ of the substances involved.
• Example of a Balanced Chemical Equation 2H2 (g)
  O2 (g) ? 2H2O (g)
• Review Reactants are on the ______ side of the
  arrow, and the
• products are on the __________ side. The arrow
  means ________,
• or reacts to produce when read aloud.
• From our example, hydrogen reacts with oxygen in
  a ______ ratio.
• The coefficients represent either the number of
  _________ or molecules present.
• The coefficients can also represent _________ if
  the substances are gases.
• (1 mole 6.02 x 1023 molecules, 1 mole of gas
  22.4 Liters)

Reactants
products
amount
left
yields
right
2 1
moles
liters
2
Common Symbols used in Chemical Equations
(See Table 8.1) used to separate 2
reactants or 2 products from each other ?
yields or reacts to produce
_____________ reaction (like a rechargeable
battery) (s) (l) (g) (aq) phase of matter
(solid, liquid, gas, or aqueous)
___________ supplied to the reaction MnO2
a catalyst, (in this case, MnO2), is used to
________ ____ the reaction. _______
given off as a product ______ precipitate
produced
reversible
heat
speed up
gas
solid
3
Decoding Common Chemical Equation Symbols
Practice Problems Describe the following
reactions using complete sentences. a) NaHCO3
(s) HCl (aq) ? NaCl (aq) H2O (l) CO2
b) H2SO4 (aq) BaCl2 (aq) ? HCl (aq)
BaSO4 (s) c) Write a chemical equation from
the following description Sodium plus bromine,
when heated, reacts to produce solid sodium
bromide.
Solid
sodium bicarbonate
plus
aqueous
hydrochloric acid
yields
aqueous
sodium chloride
plus
water
plus
carbon dioxide gas.
Aqueous
sulfuric acid
plus
aqueous
barium chloride
yields
aqueous
hydrochloric acid
plus
solid
barium sulfate.

Br2
?
NaBr (s)
Na
(s)
(l)
4
Balancing Chemical Equations

• Why do you have to balance a chemical equation?
• Law of Conservation of Matter (or Mass)
  Matter is neither ____________ nor
  _______________ in chemical reactions.
• During a chemical reaction, atoms are either
  _________, ______________, or
  rearranged. The _____________ and type of each
  atom stays the same.
• How do you balance a chemical equation?
• __________________ are placed in front of the
  substances involved in the chemical reaction to
  get the same number of atoms of each element on
  both sides of the equation. This number will
  multiply the number of atoms there are in a
  formula.

created
destroyed
joined
separated
number
Coefficients
5
Rules for Balancing Chemical Equations

• (1) Coefficients can only be placed ___ _________
  of a chemical formula.
• Practice Problems How many atoms of each type
  are indicated in
• the following compounds?
• (a) 2 (NH4)3PO4 N ___ H ___ P
  ___ O ___
• (b) 4 KC2H3O2 K ___ C ___ H ___
  O ___
• (c) 3 Ca(NO3)2 Ca ___ N ___ O
  ___

in front
6
24
2
8
4
8
12
8
3
6
18
6
Rules for Balancing Chemical Equations

• (2) You cannot change a ________________!!
• Example H2 O2 ? H2O
• To balance oxygen, you cannot change waters
  formula to_________!
• (3) You cannot place the coefficient in the
  ______________ of a formula!!
• Example Al N2 ? AlN
• To balance nitrogen, you cannot put a 2 in the
  middle to make _______.
• (4) Reduce the coefficients to the simplest
  ____________ ___ ratio.
• Example 4H2 2O2 ? 4H2O can be
  reduced to
• __H2 __O2 ? __H2O

subscript
2
2
H2O2
middle
2
2
Al2N
whole
2
1
2
7
Rules for Balancing Chemical Equations

• (5) Get rid of any ____________! Coefficients
  must be _________ s
• You cant have a _______________ of a molecule or
  atom!
• Example 1H2 ½O2 ? 1H2O changes
  to
• __ H2 __O2 ? __H2O

fractions
whole
fraction
(
)
2 x
2
1
2
8
Balancing Equations Helpful Hints

• a) Balance elements that appear in more than one
  compound ________.
• ___(NH4)2CO3 ? ___NH3 ___CO2
  ___H2O
• b) Balance _____ ___________ as though it were
  one item as long as the ion stays together as a
  group on each side of the yields arrow.
• ___Al ___CuSO4 ? ___Al2(SO4)3
  ___Cu
• c) If you cant seem to get it balanced,
  _________ _________ and begin with a different
  element the next time, or put a 2 somewhere and
  then try again.
• ___Li ___H2O ? ___LiOH ___H2
• This is what Ill constantly be telling you to do
  if you are stuck and you need my help... Pick an
  element to balance. How many are on the left
  side? How many are on the right side? ________
  ____!
• ___Fe(OH)3 ? ___Fe2O3 ___H2O

last
2
1
1
1
ion
chunks
3
2
3
1
start over
2
2
2
1
Fix it
2
3
1
9
Balancing Equations Helpful Hints

• e) My goofy balancing song may help
• If theres a ___ on the left and a ___on the
  right, you put a ___ on the
• left and a ___ on the right, (makin money!)
• ___Al ___O2 ? ___Al2O3
• f) If you see only Cs Hs and Os, balance them
  in this order C, H, O.
• ___C2H2 ___O2 ? ___CO2
  ___H2O
• ___C2H2 ___O2 ? ___CO2
  ___H2O

2
3
3
2
2
3
4
(
)
2 x
2
5/2
1
1
2
5
4
2
10
Five General Types of Reactions

• 1) ________________________
• A reaction that breaks apart ______
  ______________ into simpler substances, (usually
  two elements or an element and a smaller
  compound.)
• General Form _____ ? ___ ___
• Examples H2O ? _____ _____
• KClO3 ? _____ _____
• Remember that HONClBrIF elements are diatomic
  when alone!!

Decomposition
one compound

AX
A X
H2
O2
O2
KCl
11
Categories of Decomposition (and Composition )
Reactions
CaO
CO2

• a) carbonates ? metallic oxide CO2 CaCO3
  ? _____ _____
• b) chlorates ? metallic chloride O2
  NaClO3 ? _____ _____
• c) hydroxides ? metallic oxide H2O Mg(OH)2
  ? _____ _____
• d) oxy acids ? nonmetal oxide H2O H2SO4 ?
  _____ _____
• e) binary compounds ? 2 elements NaCl ?
  _____ _____
• Every time you try to write the formula for a
  new compound, you must look up the ___________ of
  the ions and ___________ them if they are
  different!!
• Balance it _________ you get all the correct
  formulas written first!
• Dont forget about the HONClBrIFs!

NaCl
O2
MgO
H2O
SO3
H2O
Na
Cl2
charges
cross
AFTER
12
General Types of Reactions (Continued)

• 2) _______________ (sometimes called
  Combination or Synthesis)
• A reaction of _____ __________________,
  typically a metal and a nonmetal to form ______
  ______________.
• It is the opposite of decomposition. (The same
  categories of reactions from above apply, just in
  reverse.)
• General Form ___ ___ ? _____
• Examples Al Cl2 ?
  _______
• PbO H2O ?
  ______

Composition
two substances
one compound

A
X
AX
AlCl3
2 elements ?
binary compound
Pb(OH)2
metallic water
oxide
? hydroxide
13
General Types of Reactions (Continued)

• 3) _____________ Replacement
• A reaction between ____ ______________ and ___
  ____________ that produces a different
  _____________ and ______________.
• General Forms ____ __ ? ____ __
• ____ __ ? ____ __
• The element that is trying to replace the other
  must be ________ _______________ than the one it
  is replacing.
• You must use the Activity Series to see if the
  reaction will happen.
• Table 8.2 _________ ___ more reactive
• Elements from ____ to ____ can displace hydrogen
  in water to form a metallic hydroxide and H2 gas.

Single
one compound
one element
compound
element

Y
X
AX
AY
B
A
BX
AX

more
reactive
Higher up
Li
Na
14
Activity Series
15
Single Replacement Reactions

• Examples
• NaCl F2 ? _____ _____
• FeCl2 K ? _____ _____
• HCl Zn ? _____ _____
• HCl Au ? _____ _____
• H2O Na ? _____ _____
• H2O Fe ? _____ _____
• AgNO3 Cu ? _____ _____

NaF
Cl2
KCl
Fe
ZnCl2
H2
no reaction
H2
NaOH
H(OH)
no reaction
CuNO3
Ag
16
General Types of Reactions (Continued)

• 4) _______________ Replacement (sometimes called
  Ionic)
• A reaction between _____ ________________ that
  are dissolved in water that produces _____
  ________________ , one of which is
  ________________.
• Water or a gas may be one of the two compounds
  being produced.
• General Form ____ ____ ? ____ ____
• You must use the Solubility Chart to see which
  product is the precipitate.
• Table A-7 on p.887 ___ or _____ precipitate
• Examples CaCl2 (aq) AgNO3 (aq) ?
  _________ ________
• NaOH (aq) HCl (aq) ? ________
  ________

Double
two compounds
two compounds
insoluble
AX(aq)
BY(aq)
AY(aq)
BX(s)


I
sS
Ca(NO3)2
(aq)
AgCl
(aq)
H2O (l)
NaCl
17
Double Replacement Reaction
18
General Types of Reactions (Continued)

• 5) _________________
• A reaction between a Carbon/Hydrogen (and
  sometimes Oxygen) _________________ with _____.
• The products are always the same ________
  ________
• This reaction is too easy!! Dont miss it!
• General Form CxHy O2 ? ____ ____
• Examples C2H2 O2 ? _______
  _______
• C7H6O O2 ? _______ _______

Combustion
O2
compound
CO2
H2O
CO2
H2O
CO2
H2O
CO2
H2O
19
Writing Net Ionic Equations for Double
Replacement Reactions

• A net ionic equation only shows the _________
  that were used to make the precipitate.
• Some ions were always dissolved in water. These
  are called ________________ ions. (They dont
  do anything, so we can ignore them.)
• Example CaCl2 (aq) 2AgNO3 (aq) ?
  Ca(NO3)2 (aq) 2AgCl (s)
• Ionic Equation Written as Ions Dissolved in
  Water
• ___ (aq) ___ (aq) ___ (aq) _____
  (aq) ? ___ (aq) _____ (aq) _________ (s)
• Cancel out the spectator ions, and you are left
  with the Net Ionic Equation!
• ________ _________ ? __________

ions
spectator
Ca2
2Cl-
2Ag
2NO3 -
Ca2
2NO3 -
2AgCl
2Cl-(aq)
2Ag(aq)
2AgCl(s)
20
Writing Net Ionic Equations for Double
Replacement Reactions

• Practice Problem Write the net ionic equation
  for the following reaction.
• K2CO3 (aq) Ba(NO3)2 (aq) ? _________
  _________
• Net Ionic Equation _________________________?___
  ________

KNO3
BaCO3
(aq)
CO3 -2 (aq)
Ba2 (aq)

BaCO3