Chapter 8 Section 1 Describing Chemical Reactions p. 261275

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Modern ChemistryChapter 8Chemical Equations
and Reactions
Sections 1, 2 3 Describing Chemical Reactions
Types of Chemical Reactions Activity Series of
the Elements
Chapter 8 Section 1 Describing Chemical Reactions
p. 261-275
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chemical equation precipitate coefficient
formula equation reversible reaction
Chapter Vocabulary
Chapter 8 Section 1 Describing Chemical Reactions
p. 261-275
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Section 1
Describing Chemical Reactions
Chapter 8 Section 1 Describing Chemical Reactions
p. 261-275
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Oh, That Curious Ira Remsen!
1846-1927
Chapter 8 Section 1 Describing Chemical Reactions
p. 261-275
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Oh, That Curious Ira Remsen!
This demonstration has its roots in the writings
of Ira Remsen, a 19th century professor of
chemistry at Johns Hopkins University. In his
memoir, Remsen writes.... "While reading a
textbook of chemistry I came upon the statement,
nitric acid acts upon copper. I was getting tired
of reading such absurd stuff and I was determined
to see what this meant. Copper was a more or less
familiar to me, for copper cents were then in
use.
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Oh, That Curious Ira Remsen!
"I had seen a bottle marked nitric acid on a
table in the doctor's office where I was then
doing time. I did not know its peculiarities, but
the spirit of adventure was upon me. Having
nitric acid and copper, I had only to learn what
the words acts upon meant . The statement nitric
acid acts upon copper would be something more
than mere words. All was still. In the interest
of knowledge I was even willing to sacrifice one
of the few copper cents then in my possession.
Chapter 8 Section 1 Describing Chemical Reactions
p. 261-275
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Oh, That Curious Ira Remsen!
"I put one of them on the table, opened the
bottle marked nitric acid, poured some of the
liquid on the copper and prepared to make an
observation. But what was this wonderful thing
which I beheld? The cent was already changed and
it was no small change either. A green-blue
liquid foamed and fumed over the cent and over
the table. The air in the neighborhood of the
performance became colored dark red. A great
colored cloud arose. This was disagreeable and
suffocating.
Chapter 8 Section 1 Describing Chemical Reactions
p. 261-275
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Oh, That Curious Ira Remsen!
"How should I stop this? I tried to get rid of
the objectionable mess by picking it up and
throwing it out of the window. I learned another
fact. Nitric acid not only acts upon copper, but
it acts upon fingers. The pain led to another
unpremeditated experiment. I drew my fingers
across my trousers and another fact was
discovered. Nitric acid acts upon trousers.
Chapter 8 Section 1 Describing Chemical Reactions
p. 261-275
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Oh, That Curious Ira Remsen!
" Taking everything into consideration, this was
the most impressive experiment and relatively
probably the most costly experiment I have ever
performed... It was a revelation to me. It
resulted in a desire on my part to learn more
about that remarkable kind of action. Plainly,
the only way to learn more about it was to see
its results, to experiment, to work in a
laboratory."
Chapter 8 Section 1 Describing Chemical Reactions
p. 261-275
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Demonstration
Demonstration
Ira Remsen DemoCu (s) HNO3 (aq) ? CuNO3 (aq)
H2 (g) Chemical Reactionshttp//www.metacafe.c
om/watch/650550/nitric_acid_acts_upon_a_copper_pe
nny_experiment/
Chapter 8 Section 1 Describing Chemical Reactions
p. 261-275
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Indications of a Chemical Reaction

• Proof one or more substances has changed
  identity chemical change
• Evolution of energy as heat and/or light
• Production of a gas
• Formation of a precipitate
• Color change

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Demonstration
Demonstration
Red, White and Blue Reaction http//www.chem.ox.a
c.uk/vrchemistry/FilmStudio/redwhiteblue/page01.ht
m
Chapter 8 Section 1 Describing Chemical Reactions
p. 261-275
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Characteristics of a Chemical Reaction

• The equation must represent know facts.
• The equation must contain the correct formulas
  for the reactants and products.
• Diatomic elements I2 Br2 Cl2 F2 O2 N2 H2
• Molecular elements S8 P4 (page 263)
• The law of conservation of mass must be
  satisfied.
• Coefficients a whole number that appears in
  front of a formula in a chemical equation.

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Diatomic Elements
Chapter 8 Section 1 Describing Chemical Reactions
p. 261-275
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p. 263
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Word and Formula Equations

• Word equations reactants products expressed
  in words
• methane oxygen ? carbon dioxide water

PRODUCTS
REACTANTS
YIELDS
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Word and Formula Equations

• Formula equations reactants products
  expressed with formulas not balanced
• methane oxygen ? carbon dioxide water

CH4 (g) O2 (g) ? CO2 (g)
H2O(g)
STATE OF MATTER SYMBOLS
Solid (s)Liquid (l) Gas
(g)Aqueous (aq)
? Dissolved in water
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Methane Combustion
Insert Glencoe Chemistry Concepts Applications
Disc 1
17
p. 265
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Additional Symbols
YIELDS REVERSIBLE PRECIPITATE GAS REACTANTSHE
ATED
MnO2
CATALYST ELECTROLYSISSPECIFIC TEMPSPECIFIC
PRESSURE
e-
0C
2 atm
?
heat
TABLE ON PAGE 226
Chapter 8 Section 1 Describing Chemical Reactions
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p. 226
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Additional Symbols
Chapter 8 Section 1 Describing Chemical Reactions
p. 261-275
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p. 226
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Additional Symbols
Chapter 8 Section 1 Describing Chemical Reactions
p. 261-275
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p. 226
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Balancing Chemical Equations

• If the reaction is described by a paragraph,
  write the word equation.
• Write the formula for each reactant and product
  to get the formula equation.
• Balance the equation.
• Insert state of matter symbols and other
  additional symbols.

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Balancing Chemical Equations
GOAL OF THE GAME To get the same number of atom
of each element in the reactant and the product.
To obey the law of conservation of mass.
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Balancing Chemical Equations
RULES OF THE GAME Only coefficients can be
added or changed. Once formulas are written
subscripts can not be changed.
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Balancing Chemical Equations
TIPS FOR PLAY Balance the different types of
atoms one at a time. First balance elements that
appear only once on each side. Balance
polyatomic ions that appear on both sides as a
single unit. Balance H and O last.
page 271
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Balancing Chemical Equations
TIPS FOR PLAY Try keeping a tally for each
element on each side below the equation. If it
could be balanced by a coefficient of 1½ - use
it- then multiply all coefficients in the
equation by 2.
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Sample Problem p.272
The reaction of zinc with aqueous hydrochloric
acid produces a solution of zinc chloride and
hydrogen gas. Write a balanced equation for the
reaction
Insert Holt Chemistry Visualizing Matter Disc 1
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Sample Problem p.272
zinc hydrochloric acid ? zinc chloride
hydrogen
Zn HCl ? ZnCl2 H2
2
Zn
Zn (s) 2HCl (aq) ? ZnCl2 (aq) H2 (g)
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Sample Problem p.273
Solid aluminum carbide, reacts with water to
produce methane gas, CH4, and solid aluminum
hydroxide. Write a balanced chemical equation for
this reaction.
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Sample Problem p.273
aluminum carbide water ? methane aluminum
hydroxide
Al4C3 H2O ? CH4 Al(OH)3
3
4
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Al C H O
Al C H O
4 3 2 1
1 1 7 3
4 1 16 12
4 3 24 12
4 3 24 12
Al4C3 (s) 12H2O (l) ? 3CH4 (g) 4Al(OH)3 (s)
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Sample Problem p.273
Aluminum sulfate and calcium hydroxide are used
in water-purification process. When added to
water, they dissolve and react to produce two
insoluble products, aluminum hydroxide and
calcium sulfate. These products settle out,
taking suspended solid impurities with them.
Write a balanced chemical equation for the
reaction.
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Sample Problem p.273
aluminum sulfate calcium hydroxide ? aluminum
hydroxide calcium sulfate
Al2(SO4 )3 Ca(OH)2 ? Al(OH)3 CaSO4
3
2
3
Al SO4 Ca OH
Al SO4 Ca OH
2 3 1 2
1 1 1 3
2 1 1 6
2 3 3 6
2 3 3 6
Al2(SO4)3(aq) 3Ca(OH)2(aq) ? 2Al(OH)3(s)
3CaSO4(s)
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Sample Problem
Ethane, C2H6, is a hydrocarbon which is
flammable. It combines with oxygen as it burns to
produce carbon dioxide and water vapor. Write a
balanced chemical equation for the reaction.
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Sample Problem
Ethane oxygen ? carbon dioxide and water
C2H6 O2 ? CO2 H2 O
3
2
3½
C H O
C H O
2 6 2
1 2 3
2 6 7
2 2 5
2 6 7
Multiply all coefficients by 2!
2C2H6 (g) 7O2 (g) ? 4CO2 (g) 6H2 O (g)
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Practice Problems page 272

• Write word, formula, and balanced chemical
  equations for each of the following reactions
• Magnesium and hydrochloric acid react to produc
  magnesium chloride and hydrogen.
• Aqueous nitric acid reacts with solid magnesium
  hydroxide to produce aqueous magnesium nitrate
  and water

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Practice Problems page 272
2. Solid calcium metal reacts with water to form
aqueous calcium hydroxide and hydrogen gas.
Write a balanced chemical equation for this
reaction.
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Practice Problems page 272

• Write balanced chemical equations for each of
  the following reactions
• Solid sodium combines with chlorine gas to
  produce solid sodium chloride.
• When solid copper reacts with aqueous silver
  nitrate, the products are aqueous copper (II)
  nitrate and solid silver
• In a blast furnace, the reaction between solid
  iron (III) oxide and carbon monoxide gas produces
  solid iron and carbon dioxide gas.

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Significance of a Equation
4 Fe (s) 3O2 (g) ? 2Fe2O3 (s)
4 ATOMS 3 MOLECULES 2 FORMULA UNITS
4 MOLES 3 MOLES 2 MOLES

223.4g 96.00 g 319.40g

Convert moles to grams 4mol Fe x 55.85g/1mole
223.4g
Coefficients molecules (or formula units for
ionic or atoms for elements)
Coefficients moles
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Interpreting Chemical Equations
Chapter 8 Section 1 Describing Chemical Reactions
p. 261-275
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p.269
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Section 1 Homework
Chapter 8 Section 1 Describing Chemical Reactions
p. 261-275
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