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Chapter 5Chemical Accounting
John Singer,
Jackson Community College
Chemistry for
Changing Times,
Thirteenth Edition
Lecture Outlines
© 2013 Pearson Education, Inc.
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2Chapter 5© 2013 Pearson Education, Inc.
Chemical Sentences: Equations
Chemical equations represent the sentences inthe language of chemistry. They communicate a
chemical change using symbols and formulas to
represent the elements and compounds involved in
a chemical reaction.
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3Chapter 5© 2013 Pearson Education, Inc.
Reactants are the species present before thereaction.
Products are the species present after the reaction.
Reactants→ Products
The arrow (→
) means “yield(s)” or “react(s) toproduce.”
Chemical Sentences: Equations
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4Chapter 5© 2013 Pearson Education, Inc.
The following are used to denote the state of aspecies in an equation:
(s) = solid(l) = liquid
(g) = gas
(aq) = aqueous solution
Chemical Sentences: Equations
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5Chapter 5© 2013 Pearson Education, Inc.
Coefficients are numbers used to balance achemical equation. Never change the subscripts.
Chemical Sentences: Equations
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6Chapter 5© 2013 Pearson Education, Inc.
Volume Relationships in
Chemical EquationsLaw of Combined Volumes: When all
measurements are made at the same temperature
and pressure, the volumes of gaseous reactants
and products are in a small whole-number ratios.
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Avogadro’s hypothesis: When measured at the
same temperature and pressure, volumes of all
gases contain the same number of molecules.
Volume Relationships in
Chemical Equations
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Avogadro’s Number
Avogadro’s number is defined as the
number of atoms in a
12-g sample of
carbon-12 and is
6.02 x 1023
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The Mole
A mole (mol) is defined as the amount of asubstance that contains 6.02 x 1023 particles.
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The Mole
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Formula mass is the average mass of a formulaunit relative to that of a carbon-12 atom.
It is simply the sum of the atomic masses for all
atoms in a formula.
If the formula represents a molecule, often the
term molecular mass is used.
The Mole
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The Mole
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13Chapter 5© 2013 Pearson Education, Inc.
Molar volume of a gas: One mole of any gasoccupies a volume of 22.4 L at standard
temperature and pressure (STP).
STP is defined as 1 atmosphere (atm) of pressure
and a temperature of 0 oC.
The Mole
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14Chapter 5© 2013 Pearson Education, Inc.
Mole and Mass Relationships in
Chemical EquationsStoichiometry involves the quantitative
relationship between reactants and products in a
balanced chemical equation.
The coefficients of a balanced chemical equation
represent moles.
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15Chapter 5© 2013 Pearson Education, Inc.
2 H2 + O2 2 H2O
This equation can be read as follows:
2 mol of H2 reacts with one mol O2 to yield
2 mol of H2O.
Mole and Mass Relationships in
Chemical Equations
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16Chapter 5© 2013 Pearson Education, Inc.
Steps in a Stoichiometric Calculation:
1.Write and balance the chemical equation for thereaction.
2.Determine molar masses of substances involvedin the calculation.
3.Use the coefficients of the balanced equation toconvert the moles of the given substance to the
moles of the desired substance.4.Use the molar mass to convert the moles of thedesired substance to grams of the desiredsubstance.
Mole and Mass Relationships in
Chemical Equations
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18Chapter 5© 2013 Pearson Education, Inc.
Solutions
The amount of solute in a given amount ofsolvent is defined as solution concentration.
A dilute solution contains relatively small
amounts of solute in a given amount of solvent.
A concentrated solution contains relatively
large amounts of solute in a given amount ofsolvent.
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19Chapter 5© 2013 Pearson Education, Inc.
Molarity (M) is defined as the moles of soluteper liter of solution.
M =liter
mol
Solutions
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20Chapter 5© 2013 Pearson Education, Inc.
Percent Concentration
Percent by volume =solutionof volume
soluteof volumex 100
Solutions