1. Chemical Equations & Reactions
CHAPTER 8
Chemical Equations & Reactions

2. Chemical Equations Represented w/ symbols & formulas
Identifies reactants & products
Identifies amounts of each

3. What Do They Tell Us?

4. Signs of a Chemical Reaction
Chapter 8
Visual Concepts
Signs of a Chemical Reaction

5. Chapter 8
Visual Concepts
Precipitate

6. Evidence of a Chemical Reaction
Section 1 Describing Chemical Reactions
Chapter 8
Evidence of a Chemical Reaction
solution color changes
solution bubbles
copper is used up

7. Evidence of a Chemical Reaction
Produces heat and/or light
Produces gas
Forms a precipitate (a solid appears)
Color change
Temperature change

8. Balancing Chemical Reactions
Why do it?
We need to know exactly how much of everything there is. (Ch. 9 Stuff)
What do you do?
Count
Make sure the exact same number of atoms exists on both sides of the eqn.

9. Reading a Chemical Equation
Chapter 8
Visual Concepts
Reading a Chemical Equation

10. Balancing a Chemical Equation by Inspection

11. Rules of Balancing
Write each individual formula (Criss-Cross Applesauce)
Take inventory
Use coefficients to balance.
Check your work.

12. H2O two hydrogens / 1 oxygen
Coefficients
#’s that go in front
They multiply
Example
H2O two hydrogens / 1 oxygen
2 H2O 4 hydrogens/ 2 oxygens
5 H2O
10 hydrogens / 5 oxygens

13. Sample Problem A
Na + Cl2  NaCl 1

14. Sample Problem A
Na + Cl2  NaCl

15. Sample Problem A
Na + Cl2  NaCl

16. Sample Problem A Na + Cl2  NaCl 1 2 1 1 Cl are not equal.
Cl are not equal.
Use a coefficient!

17. Sample Problem A
Na + Cl2  2 NaCl
Now count again!

18. Sample Problem A
Na + Cl2  2 NaCl 1

19. Sample Problem A
Na + Cl2  2 NaCl

20. Sample Problem A
Na + Cl2  2 NaCl

21. Sample Problem A Na + Cl2  2 NaCl 1 2 2 2
Now the Na atoms aren’t equal!
Use another coefficient.

22. Sample Problem A
2 Na + Cl2  2 NaCl

23. Sample Problem A
2 Na + Cl2  2 NaCl 2

24. Sample Problem A
2 Na + Cl2  2 NaCl

25. Now everything is EQUAL!
Sample Problem A
2 Na + Cl2  2 NaCl
Now everything is EQUAL!
2 Na + Cl2  2 NaCl

26. Ca3(PO4)2 + Mg(OH)2 → Ca(OH)2 + Mg3(PO4)2
Sample Problem B
Ca3(PO4)2 + Mg(OH)2 → Ca(OH)2 + Mg3(PO4)2
COUNT!
Ca 3
P 2
Mg 1
H 2
O = 10
Ca 1
P 2
Mg 3
H 2
O = 10

27. Ca3(PO4)2 + Mg(OH)2 → 3 Ca(OH)2 + Mg3(PO4)2
Sample Problem B
Ca3(PO4)2 + Mg(OH)2 → 3 Ca(OH)2 + Mg3(PO4)2
Ca 3
P 2
Mg 3
H 6
O = 14
Ca 3
P 2
Mg 1
H 2
O = 10

28. Ca3(PO4)2 + 3 Mg(OH)2 → 3 Ca(OH)2 + Mg3(PO4)2
Sample Problem B
Ca3(PO4)2 + 3 Mg(OH)2 → 3 Ca(OH)2 + Mg3(PO4)2
Ca 3
P 2
Mg 3
H 6
O = 14
Ca 3
P 2
Mg 3
H 6
O = 14

29. Special Rules If it’s a metal by itself, just write the symbol.
Copper Cu
If it’s a nonmetal by itself, write the symbol with a subscript 2.
Nitrogen N2
Leave Oxygen for last!

30. Paint Can Demo
What did I do?

31. Paint Can Demo

32. Types of Chemical Reactions

33. Chapter 8
Visual Concepts
Synthesis Reactions

34. Synthesis Reactions Smaller compounds make one bigger one A + B  AB
Example:
Na + Cl  NaCl

35. Decomposition Reaction
Chapter 8
Visual Concepts
Decomposition Reaction

36. Decomposition Larger compounds break down to smaller ones
Opposite of synthesis reaction
AB  A + B
Example:
2 KClO3  2 KCl + 3 O2

37. Single Displacement Reaction
Chapter 8
Visual Concepts
Single Displacement Reaction

38. Single Replacement Reaction
One atom changes places with another atom
A + BC  AC + B
Example:
Zn + 2 HCl  H2 + ZnCl2

39. Double-Displacement Reaction
Chapter 8
Visual Concepts
Double-Displacement Reaction

40. Double Replacement Reaction
Two atoms trade places
AB + CD  AD + CB
Example:
2 KI + Pb(NO3)2  2 KNO3 + PbI2

41. Precipitation Reaction
Chapter 8
Visual Concepts
Precipitation Reaction

42. Chapter 8
Visual Concepts
Combustion Reaction

43. Combustion Reaction
Anything reacting with O2
X + O2  CO2 + H2O

44. 1. What type of chemical reaction involves the exchange of the ions of two compounds in an aqueous solution to form two new compounds?
A. synthesis reaction
B. decomposition reaction
C. single-displacement reaction
D. double-displacement reaction

45. 1. What type of chemical reaction involves the exchange of the ions of two compounds in an aqueous solution to form two new compounds?
A. synthesis reaction
B. decomposition reaction
C. single-displacement reaction
D. double-displacement reaction

46. 2. Which of these sentences correctly states the law of conservation of mass?
F. In a chemical reaction, the mass of the products cannot exceed the mass of the reactants.
G. In a chemical reaction, the mass of the products is always equal to the mass of the reactants.
H. In a chemical reaction, the mass of the products is always less than the mass of the reactants.
I. In a chemical reaction, the mass of the products is always greater than the mass of the reactants.

47. 2. Which of these sentences correctly states the law of conservation of mass?
F. In a chemical reaction, the mass of the products cannot exceed the mass of the reactants.
G. In a chemical reaction, the mass of the products is always equal to the mass of the reactants.
H. In a chemical reaction, the mass of the products is always less than the mass of the reactants.
I. In a chemical reaction, the mass of the products is always greater than the mass of the reactants.

48. 3. Of these reaction types, which has only one reactant?
A. decomposition
B. displacement
C. oxidation
D. synthesis

49. 3. Of these reaction types, which has only one reactant?
A. decomposition
B. displacement
C. oxidation
D. synthesis