Chapter 7 Chemical Reactions 7.2 Chemical Equations Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

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) CO2 (g) C(s) Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

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

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

Symbols Used in Equations Symbols are used in equations to show The states of the reactants. The states of the products. The reaction conditions. Table 7.2 Copyright © 2008 by Pearson Education, Inc. Publishing as Benjamin Cummings

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 coefficients 2Al + 3S Al2S3 Balanced 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)

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) 4 P 4 P 12 Br 12 Br B. 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s) 2 Al 2 Al 2 Fe 2 Fe 3 O 3 O

Learning Check Determine if each equation is balanced or not. A. Na(s) + N2(g) → NaN3(s) B. C2H4(g) + 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 = 2 C 6 H = 6 H 1 O = 1 O