Chapter 10: Chemical Reactions

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Chapter 10 Chemical Reactions
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Chemical Reactions

• Defn process by which the atoms of one or more
  substances are rearranged
• - new substances are formed

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Evidences of a chemical reaction

• 1) gas production
• 2) light production
• 3) temperature change (endo/exothermic)
• 4) precipitate formed (solid from 2 liquids)
• 5) permanent color change

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• Energy is stored in compounds as chemical
  potential energy due to specific arrangements of
  atoms. A chemical reaction changes the potential
  energy present. When energy is lost as heat, it
  is called a __________________. These reactions
  get hotter. Sometimes energy is gained heat is
  added for a reaction to occur. These are called
  ______________________, which get colder.

exothermic reaction
endothermic reaction
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Word Equation

• Defn equation expressed in words

Iron chlorine ? iron (III) chloride
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Formula Equation

• Defn equation with chemical formulas
• Coefficients whole placed in front of
  compound
• Balances the number of atoms

2 Fe 3 Cl2 ? 2 FeCl3
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Parts Of A Reaction

• Symbols

heat added
(s)
solid
?
(l)
liquid
(g)
gas
(aq)
aqueous (dissolved in water)
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example

• Solid calcium carbonate reacts with a solution of
  hydrochloric acid to produce aqueous calcium
  chloride, gaseous carbon dioxide, and liquid water

HCl (aq)
CaCO3 (s)
CaCl2 (aq)
CO2 (g)
H2O (l)
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Diatomic Elements

• Defn 7 elements that NEVER occur as singular
  atoms (always paired with an the same or
  different element)

H2 O2 F2 Br2 I2 N2 Cl2
Ex 2 HCl K ? 2 KCl H2
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Balancing Equations

• Number of reactant atoms on left of an element
  must equal number of product atoms on the right
• Must obey law of conservation of mass

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Rules for balancing equations

• 1) Only coefficients are changed in balancing
  reactions
• 2) Never change subscript during balancing
• 3) Coefficients are placed in front of compound
  and multiplied across compound to get total of
  atoms of each element

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Helpful Hints

• Balance hydrogen and oxygen last
• Balance polyatomic ions as a group if present on
  both reactants and products

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• Before
• After

MgCl2 NaOH ? Mg(OH)2 NaCl
1 Mg
1 Na
1 Mg
1 Na
2 Cl
1 Cl
1 OH
2 OH
MgCl2 2 NaOH ? Mg(OH)2 2 NaCl
1 Mg
2 Na
1 Mg
2 Na
2 Cl
2 Cl
2 (OH)
2 (OH)
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Sample Problems

• sodium and chlorine combine to form sodium
  chloride

?
Cl2
NaCl
1
2
2
Na
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Sample Problems

• sodium hydroxide and calcium bromide react to
  produce calcium hydroxide and sodium bromide

2
1
NaOH
CaBr2

?
1
Ca(OH)2
NaBr

2
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Sample Problems

• aluminum sulfate and calcium hydroxide produce
  calcium sulfate and aluminum hydroxide

1
3
Al2(SO4)3
Ca(OH)2

?
2
3
CaSO4
Al(OH)3

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Classifying Chemical Reactions

• Synthesis
• Decomposition
• Single replacement
• Double Replacement
• Combustion

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Synthesis

• Defn two or more substances react to form ONE
  product
• A B ? AB

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Hey baby lets get jiggy.
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Synthesis

• reaction of two elements

2
2
3
___Al ___Cl2 ?
___AlCl3
Al3
Cl1-
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Synthesis

• reaction of two compounds
• reaction of element and compound

CaO H2O ?
Ca(OH)2
SO2 O2 ?
SO3
2
2
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Decomposition

• defn one substance breaks down into two or
  more simpler products

AB ? A B
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Break yoself fool!
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Decomposition

• Ex reaction

2
2
3
__ NaN3 (s) ?
___ Na (s)
___ N2 (g)
2
2
1
__ CaO (s) ?
___ Ca (s)
___ O2 (g)
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Single Replacement Reactions

• Defn one element replaces another element in a
  compound to form new compound

A BX ?
AX B
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Im gon dance with yo lady
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Reactivity Series

• metals
• halogens

Li K Ca Na Mg Al Mn Zn Fe Ni Sn Pb H Cu Ag Au
most active
least active
F Cl Br I
most active
least active
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examples

• aluminum iron (III) oxide

Fe3
O2-
Stronger?
2
2
1
1

Al

Fe2O3
Al2O3
Fe
Al3
O2-
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examples

• silver copper (I) nitrate

Cu1
NO31-
Stronger?
Ag

CuNO3
NO RXN
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examples

• fluorine gas sodium bromide

Stronger?
2
2
1
1
F2

NaBr
Br2
NaF

Na1
F1-
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examples

• chlorine gas hydrogen fluoride

Stronger?
Cl2
HF

NO RXN
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Double Replacement

• Defn exchange of cations between two ionic
  compounds

A B C D ?
AD CB
switch
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(No Transcript)
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3 possible products of double replacement rxns

• Precipitate
• Gas
• Water

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Ex problem

• lithium iodide and aqueous silver nitrate react

Li1
I1-
Ag1
NO31-
Li I
Ag I (s)
AgNO3
LiNO3


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Combustion

• defn compound reacts with O2
• Hydrocarbon cmpd w/ only carbon and hydrogen

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Combustion

• Combustion of hydrocarbons
• ALWAYS produces CO2 and H2O

CxHy O2
CO2 H2O
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Ex problem

• show combustion of propane (C3H8) gas

C3H8
O2
CO2
H2O


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