chemistry
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11.1
Describing Chemical Reactions
On May 6, 1937, the huge airship
Hindenburg erupted into a fireball.
Within a short time, 210,000 cubic
meters of hydrogen had burned and
the airship was destroyed. The
chemical reaction that occurred is
“hydrogen combines with oxygen to
produce water.” You will learn to
represent this chemical reaction by a
chemical equation.
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11.1
Describing Chemical
Reactions
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Writing Chemical Equations
Writing Chemical Equations
How do you write a word equation?
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11.1
Describing Chemical
Reactions
>
Writing Chemical Equations
Word Equations
To write a word equation, write the
names of the reactants to the left of the
arrow separated by plus signs; write the
names of the products to the right of the
arrow, also separated by plus signs.
Reactant + Reactant  Product + Product
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11.1
Describing Chemical
Reactions
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Writing Chemical Equations
Methane + Oxygen  Carbon dioxide + Water
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11.1
Describing Chemical
Reactions
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Writing Chemical Equations
iron + oxygen → iron(III) oxide
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11.1
Describing Chemical
Reactions
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Writing Chemical Equations
Hydrogen Peroxide  Water and Oxygen
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11.1
Describing Chemical
Reactions
>
Writing Chemical Equations
Chemical Equations
A chemical equation is a representation of a
chemical reaction; the formulas of the reactants
(on the left) are connected by an arrow with the
formulas of the products (on the right).
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11.1
Describing Chemical
Reactions
>
Writing Chemical Equations
How do you write a skeleton equation?
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11.1
Describing Chemical
Reactions
>
Writing Chemical Equations
Write the formulas of the reactants to
the left of the yields sign (arrow) and
the formulas of the products to the
right.
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11.1
Describing Chemical
Reactions
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Writing Chemical Equations
A skeleton equation is a chemical equation
that does not indicate the relative amounts
of the reactants and products.
Here is the equation for rusting:
Fe + O2  Fe2O3
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11.1
Describing Chemical
Reactions
>
Writing Chemical Equations
A catalyst is a substance that speeds up the
reaction but is not used up in the reaction.
Without Catalyst
With Catalyst
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11.1
Describing Chemical
Reactions
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Writing Chemical Equations
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Describing Chemical
Reactions
>
Writing Chemical Equations
Animation 12
Relate chemical symbols and formulas to the
information they communicate.
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Practice Problems for Conceptual Problem 11.1
Problem Solving 11.2 Solve Problem
2 with the help of an interactive guided
tutorial.
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11.1
Describing Chemical
Reactions
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Balancing Chemical Equations
Balancing Chemical Equations
What are the steps in writing a balanced
chemical equation?
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11.1
Describing Chemical
Reactions
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Balancing Chemical Equations
To write a balanced chemical equation,
first write the skeleton equation. Then
use coefficients to balance the equation
so that it obeys the law of conservation
of mass.
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11.1
Describing Chemical
Reactions
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Balancing Chemical Equations
This is a balanced equation for making a bicycle.
The numbers are called coefficients—small
whole numbers that are placed in front of the
formulas in an equation in order to balance it.
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11.1
Describing Chemical
Reactions
>
Balancing Chemical Equations
A chemical reaction is also described by a
balanced equation in which each side of the
equation has the same number of atoms of each
element and mass is conserved.
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Describing Chemical
Reactions
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Balancing Chemical Equations
Simulation 11
Sharpen your skills by balancing chemical
equations.
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Practice Problems for Conceptual Problem 11.2
Problem Solving 11.4 Solve Problem
4 with the help of an interactive guided
tutorial.
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