Download 7.2 Chemical Eqns PPT

Chapter 7 Chemical
Reactions
7.2 Chemical Equations
Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
1
Chemical Equations
A chemical equation
• Gives the chemical formulas of the reactants
on the left of an arrow and the products on the
right.
Reactants
Product
O2(g)
C(s)
Copyright © 2008 by Pearson Education,
Inc. Publishing as Benjamin Cummings
2
CO2 (g)
Chemical Equations are
Balanced
In a balanced chemical reaction
• Atoms are not gained or lost.
Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
3
Chemical Equations are
Balanced
In a balanced chemical reaction
• The number of reactant atoms is equal to the
number of product atoms.
Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
4
Symbols Used in Equations
Symbols are used in
equations to show
Table 7.2
• The states of the
reactants.
• The states of the
products.
• The reaction
conditions.
Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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A Balanced Chemical Equation
In a balanced chemical equation,
• There must be the same number of each type
of atom on the reactant and on the product
sides of a balanced equation.
• Numbers called coefficients are used in front of
one or more formulas.
Al
+
S
Al2S3
Not Balanced
Al2S3
Balanced
coefficients
2Al + 3S
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2Al
=
2Al
3S
=
3S
Learning Check
State the number of atoms of each element on the
reactant and on the product sides of the equations:
A. P4(s) + 6Br2(l) → 4 PBr3(g)
B. 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s)
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Solution
State the number of atoms of each element on the
reactant and on the product sides of the equations:
A. P4(s) + 6Br2(l) → 4PBr3(g)
4P
4P
12 Br
12 Br
B. 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s)
2 Al
2 Al
2 Fe
2 Fe
3O
3O
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Learning Check
Determine if each equation is balanced or not.
A. Na(s) + N2(g) → NaN3(s)
B. C2H4(g)
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+ H2O(l) → C2H5OH(l)
Solution
Determine if each equation is balanced or not.
A. Na(s) + N2(g) → NaN3(s)
No. 2N on reactant side, 3N on product side.
B. C2H4(g) + H2O(l) → C2H5OH(l)
Yes. 2 C
= 2C
6H
= 6H
1O
= 1O
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