1. Chapter 8 Chemical Reactions
8.1 Equations for Chemical Reactions
Learning Goal Identify a balanced chemical equation and determine the number of atoms in the reactants and products.
© 2014 Pearson Education, Inc.

2. Writing Ionic Formulas (6.2, 6.4) Naming Ionic Compounds (6.3, 6.4)
Chapter 8 Readiness
Key Math Skills
Solving Equations (1.4D)
Core Chemistry Skills
Writing Ionic Formulas (6.2, 6.4)
Naming Ionic Compounds (6.3, 6.4)
Writing the Names and Formulas for Molecular Compounds (6.5)
© 2014 Pearson Education, Inc.

3. Chemical Change
A chemical change occurs when a substance is converted into one or more new substances.
When silver tarnishes, silver metal (Ag) reacts with sulfur (S) to form a black substance we call tarnish (Ag2S).

4. Chemical Reaction
A chemical reaction
involves chemical change
represents the formation of a new substance with new properties
Dropping an antacid tablet in water produces CO2 gas when NaHCO3 reacts with citric acid (C6H8O7).

5. Visual Evidence of a Chemical Reaction
The following evidence is an indication that a chemical reaction may have occurred.
A chemical equation tells us the materials needed and the products formed in a chemical reaction.

6. Writing a Chemical Reaction
When charcoal is burned in a grill, the carbon in charcoal combines with oxygen from the air to form water and carbon dioxide gas.

7. Chemical Equations
In chemical equations
reactants are written on the left, products on the right
two or more formulas on one side are separated by a (+) sign
the delta sign, (Δ), indicates heat is used to start the reaction
physical states are abbreviated, including solid (s), liquid (l), gas (g), and aqueous (aq)

8. Chemical Equations

9. Learning Check
Identify the visible evidence of a chemical reaction in each of the following:
A. Methane gas in an outdoor heater burns with a blue flame.
B. Bleach removes stains from a shirt.
C. Bubbles of CO2 are released when baking soda is mixed with vinegar.

10. A. Methane gas in an outdoor heater burns with a blue flame.
Solution
Identify the visible evidence of a chemical reaction in each of the following:
A. Methane gas in an outdoor heater burns with a blue flame.
heat and a flame
B. Bleach removes stains from a shirt. color change (color removed)
C. Bubbles of CO2 are released when baking soda is mixed with vinegar. formation of a gas (bubbles)

11. Identifying a Balanced Equation
Every chemical reaction is written as a balanced equation, such that atoms of each element are the same in the reactants and products.
To balance a reaction, coefficients are written in front of chemical formulas.
2H2(g) + O2(g)  2H2O(g)

12. Balanced Chemical Equations

13. Learning Check
State the number of atoms of each element on the reactant and the product sides of the equations.
A. P4(s) + 6Br2(l) → 4PBr3(g)
B. 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s)

14. Solution
State the number of atoms of each element on the reactant and the product sides of the equations.
A. P4(s) + 6Br2(l) → 4PBr3(g)
4 P P
12 Br 12 Br

15. Solution
State the number of atoms of each element on the reactant and the product sides of the equations.
B. 2Al(s) + Fe2O3(s) → 2Fe(s) + Al2O3(s)
2 Al 2 Al
2 Fe 2 Fe
3 O 3 O

16. Learning Check
Determine if each equation is balanced or not.
A. Na(s) + N2(g) → NaN3(s)
B. C2H4(g) + H2O(l) → C2H5OH(l)

17. Solution
Determine if each equation is balanced or not.
A. Na(s) + N2(g) → NaN3(s)
1 Na Na
2 N 3 N Equation is not balanced.

18. Solution
Determine if each equation is balanced or not.
B. C2H4(g) + H2O(l) → C2H5OH(l)
2 C 2 C
6 H 6 H
1 O 1 O Equation is balanced.