General organic and biological chemistry structures off life 5th CH7 chemical reactions and quantities GOB structures 5th ed

Lecture Presentation

Chapter 7
Chemical
Reactions
and Quantities
Karen C. Timberlake
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Chapter 7 Chemical Reactions and
Quantities
A dental hygienist cleans and
polishes teeth and may take
X-rays of the patients’ teeth.
The hygienist must be
knowledgeable about proper
safety procedures and how
to protect against disease
transmission.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Chapter 7 Readiness

Key Math Skills
• Calculating a Percentage (1.4C)
• Solving Equations (1.4D)
• Writing Numbers in Scientific Notation (1.4F)

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Chapter 7 Readiness
Core Chemistry Skills
• Counting Significant Figures (2.2)
• Using Significant Figures in Calculations (2.3)
• Writing Conversion Factors from Equalities (2.5)
• Using Conversion Factors (2.6)
• Using Energy Units (3.4)
• Writing Ionic Formulas (6.2)
• Naming Ionic Compounds (6.3)
• Writing the Names and Formulas for Molecular
Compounds (6.5)
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


7.1 Equations for Chemical Reactions
A chemical change

occurs when a
substance is converted
into one or more new
substances that have
different formulas and
different properties.

Chemical reactions involve chemical
changes. When iron (Fe) reacts with
oxygen (O2), the product is rust, (Fe2O3).

Learning Goal Write a balanced chemical equation from the
formulas of the reactants and products for a reaction; determine
the number of atoms in the reactants and products.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Chemical Changes
A chemical change
• occurs when a substance
is converted into one or
more substances with
different formulas and
different properties.
• may be observed by the
formation of bubbles, a
change in color, production

of a solid, or heat that is
produced or absorbed.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

A chemical change produces new
substances with new properties.
© 2016 Pearson Education, Inc.


Writing a Chemical Equation

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Symbols Used in Chemical Equations
To write a chemical equation,
• an arrow separates reactants from the products ().
• reactants are written on the left side of the arrow;
products are written on the right side of the arrow.
• multiple reactants or products are separated by a +
sign.
• the delta (Δ) sign indicates heat is used to start the
reaction.
Δ
reactant + reactant
product + product

• physical states of compounds are denoted in
parentheses following the compound: solid (s), liquid (l),
gas (g), and aqueous (aq) or dissolved in water.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Symbols Used in Writing Equations

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Identifying a Balanced Equation
In a balanced chemical equation,
• no atoms are lost or gained.
• the number of atoms on the reactant side is equal to the
number of atoms on the product side for each element.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.

Guide to Balancing a Chemical Equation

Core Chemistry Skill Balancing a Chemical Equation
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Balancing a Chemical Equation: Formation
of Al2S3
STEP 1 Write an equation using the correct formulas of
the reactants and products.
Al(s) + S(s)  Al2S3(s)
STEP 2 Count the atoms of each element in the reactants
and products.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Balancing a Chemical Equation: Formation
of Al2S3
STEP 3 Use coefficients to balance each element. Starting
with the most complex formula, change coefficients to
balance the equation.
2Al(s) + 3S(s) 

Al2S3(s)

STEP 4 Check the final equation to confirm it is balanced.
Make sure coefficients are the lowest ratio.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Study Check
State the number of atoms of each element on the
reactant side and the product side for each of the following
balanced equations.
A. P4(s) + 6Br2(l)  4PBr3(g)
B. 2Al(s) + Fe2O3(s)  2Fe(s) + Al2O3(s)

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Solution
State the number of atoms of each element on the
reactant side and the product side for each of the following
balanced equations.
A. P4(s) + 6Br2(l)  4PBr3(g)

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Solution
State the number of atoms of each element on the
reactant side and the product side for each of the
following balanced equations.
B. 2Al(s) + Fe2O3(s)  2Fe(s) + Al2O3(s)

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Study Check
Balance the chemical equation when solid Fe3O4 reacts with
hydrogen gas to produce solid iron and water.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Solution
Balance the chemical equation when solid Fe3O4 reacts with

hydrogen gas to produce solid iron and water.

STEP 1 Write an equation using the correct formulas of
the reactants and products.
Fe3O4(s) + H2(g)  Fe(s) + H2O(l)

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Solution
Balance the chemical equation when solid Fe3O4 reacts with
hydrogen gas to produce solid iron and water.
Fe3O4(s) + H2(g)  Fe(s) + H2O(l)
STEP 2 Count the number of atoms of each element in
the reactants and products.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Solution
Balance the chemical equation when solid Fe3O4 reacts with
hydrogen gas to produce solid iron and water.
Fe3O4(s) + 4H2(g)  3Fe(s) + 4H2O(l)
STEP 3 Use coefficients to balance each element.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Solution
Balance the chemical equation when solid Fe3O4 reacts with
hydrogen gas to produce solid iron and water.
Fe3O4(s) + 4H2(g)  3Fe(s) + 4H2O(l)
STEP 4 Check the final equation to confirm it is balanced.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Balancing with Polyatomic Ions

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Balancing with Polyatomic Ions
Balance the following chemical equation:
Na3PO4(aq) + MgCl2(aq)  Mg3(PO4)2(s) + NaCl(aq)

STEP 1 Write an equation using the correct formulas of
the reactants and products.
Na3PO4(aq) + MgCl2(aq)  Mg3(PO4)2(s) + NaCl(aq)
Unbalanced

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Balancing with Polyatomic Ions
STEP 2 Count the atoms of each element in the reactants
and products. Balance the phosphate ion as a unit.
Na3PO4(aq) + MgCl2(aq)  Mg3(PO4)2(s) + NaCl(aq)

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Solution
STEP 3 Use coefficients to balance each element.
2Na3PO4(aq) + 3MgCl2(aq)  Mg3(PO4)2(s) + 6NaCl(aq)

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.