1. Balancing Chemical Equations and Types of Chemical Reactions
Unit 4 1

2. What is a chemical equation?
Parts of an equation:
2Ag + H2S
Ag2S + H2
Reaction symbol

3. Reactants and Products3

4. Subscripts and Coefficients‏
Coefficient - 4

6. 2H2 + O2 → 2H2O 6

7. Law of Conservation of Mass
In a chem. rxn, matter is
If an equation obeys the Law of Conservation, 7

8. Choosing the order of balancing
Start
Save for later
Pb + PbO2 + H+ → Pb2+ + H2O
Start Elements that appear only 1 time per side
Start
Save for later
To balance this equation, use the order: O, H, Pb

9. Rules of Balancing 1. 9

10. Rules of Balancing
A few extra tips: 10

11. . CH4 + O2 → CO2 + H2O 1 carbon atom 4 hydrogen atoms 2 oxygen atoms11

12. CH4 + O2 → CO2 + H2O 1 carbon atom 4 hydrogen atoms 4 oxygen atoms12

13. DO NOW: What are the reactants in this chemical equation?
C O → CO2
1 Carbon atom oxygen molecule → carbon dioxide molecule
What are the reactants in this chemical equation?
What are the products in this chemical equation?
Are there the same number of atoms on both sides of the equation?
Where any atoms destroyed or created?
Was the Law of Conservation of Matter maintained?

15. Balancing Equations _ _ 2 1 2 3 N2 + H2 → NH3 N H
Balance the following equation by adjusting coefficients.
N H2 → NH3 _ _
reactants
products N 2 1 2 3 H 15

16. Balancing Equations 3 2 2 2 1 6 2 6 3 N2 + H2 → NH3 N H
Balance the following equation by adjusting coefficients.
N H2 → NH3 3 2
reactants
products N 2 2 1 6 2 6 3 H 16

17. Balancing Equations _ _ 1 1 1 1 3 2 KClO3 → KCl + O2 K Cl O
Balance the following equation by adjusting coefficients. _
KClO3 → KCl + O2 _
reactants
products K 1 1 Cl 1 1 3 2 O 17

18. Balancing Equations 3 2 2 2 1 1 2 2 1 2 1 6 3 2 6 KClO3 → KCl + O2 K
Balance the following equation by adjusting coefficients. 3 2
KClO3 → KCl + O2 2
reactants
products K 2 1 1 2 Cl 2 1 2 1 6 3 2 6 O 18

19. DO NOW: Is this equation balanced?
3 H2SO4 + 2 B(OH)3 → B2 (SO4) H2O If not, balance it!

20. Balancing Equations
Balance the following equation: __C2H6 + __ O2 → __ CO2 + __ H2O 20

21. __Fe + __ O2 → __ Fe2O3 Balancing Equations
Balance the following equation:
__Fe + __ O2 → __ Fe2O3 21

22. Balancing Equations Balance the following equation:
__ HCl + __ Ca(OH)2 → __ CaCl2 + __ H2O
__ H2 + __ O2 → __ H2O
____ P4 + ____ O2 → ____ P2O3 22

23. DO NOW Balance the following equation:
___ Ga + ___ H2SO ___ Ga2(SO4)3 + ___ H2 23

24. 5 Types of Chemical Reactions

25. Combination A+ B → AB

26. Decomposition AB → A + B

27. Single Displacement

29. Double Displacement AB + CD → CB + AD

31. Combustion

32. Activity Series

34. Examples
Mg + Cu(NO3)2 →
Fe + NA2SO4 →
Zn + MnCl2 →
2Al + 3SnSO4 →

35. Examples 2Al + 3SnSO4 → Mg + Cu(NO3)2 → Mg(No3)2 + Cu
Fe + Na2SO4 → no rxn
Zn + MnCl2 → no rxn
2Al + 3SnSO4 →
Al2(SO4)3 + 3 SN

36. DO NOW:
Will a reaction occur in the following single displacement reactions? If yes, write the products…
Fe + Al2O3 →
Ca + 2HCl →

37. The Mole

38. The Mole … what is it? Abbreviation for the mole: mol
A mole is defined as the number of atoms in exactly 12 grams of carbon- 12
The number is called Avogadro’s Number
One mole of carbon atoms has a mass of 12 grams
Abbreviation for the mole: mol

39. A Mole of Particles Contains 6.02 x 1023 particles
1 mole C = 6.02 x 1023 C atoms
1 mole H2O = 6.02 x H2O molecules
1 mole NaCl = 6.02 x NaCl molecules

40. What does a mole count in?
Avogadro’s Number: x 1023 “things” = 1 mole
6.02 × 1023 = 602,000,000,000,000,000,000,000 !
“mole”
6.02 × 1023
1 mole of doughnuts
6.02 × 1023 doughnuts
1 mole of atoms
6.02 × 1023 atoms
1 mole of molecules
6.02 × 1023 molecules
This means a 12 ounce bottle of water would have
19.7 “moles” of water…a much easier-to-work-with number!

41. Converting to Molar Mass
Molar Mass: The mass for one mole of an atom of molecule
Other terms commonly used for the same meaning:
Molecular Weight
Molecular Mass
Formula Weight
Formula Mass

42. Unit for molar mass: g/mole or g/mol
Mass of 1 Mole of Atoms
The average atomic mass = grams for 1 mole Average atomic mass found on periodic table
Element
Mass
1 mole of carbon atoms
12.01 g
1 mole of oxygen atoms
16.00 g
1 mole of hydrogen atoms
1.01 g
Unit for molar mass: g/mole or g/mol

43. Calculating a Molecule’s Mass
To find the molar mass of a molecule: 1
Count the number of each type of atom 2
Find the molar mass of each atom on the periodic table 3
Multiple the # of atoms × molar mass for each atom 4
Find the sum of all the masses

44. Example Problem - Molar Mass
Find the molar mass for CaBr2

45. Example Problem - Molar Mass
Count the number of each type of atom 1
Example:
Find the molar mass for CaBr2
Ca 1
Br 2

46. Example Problem - Molar Mass2
Find the molar mass of each atom on the periodic table
Example:
Find the molar mass for CaBr2
Ca g/mole
Br g/mole

47. Example Problem - Molar Mass
Multiply the # of atoms x molar mass for each atom 3
Example:
Find the molar mass for CaBr2
Ca x = g/mole
Br x = g/mole

48. Example Problem - Molar Mass
Find the sum of all the masses 4
Example:
Find the molar mass for CaBr2
Ca x = g/mol
Br x = g/mol
g/mol
1 mole of CaBr2 molecules would have a mass of g

49. Example of Molar Mass and Parenthesis
Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis.
Example:
Find the molar mass for Sr(NO3)2

50. Example of Molar Mass and Parenthesis
Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis.
Example:
Find the molar mass for Sr(NO3)2 Sr 1 ×
87.62 g/mole =
87.62 g/mole N 2 ×
14.01 g/mole =
28.02 g/mole O 6 ×
16.00 g/mole = +
96.00 g/mole
g/mole
1 mole of Sr(NO3)2 molecules would have a mass of g

51. Example of Molar Mass and Parenthesis
Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis.
Example:
Find the molar mass for Al(OH)3

52. Example of Molar Mass and Parenthesis
Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis.
Example:
Find the molar mass for Al(OH)3 Al 1 ×
26.98 g/mole =
26.98 g/mole O 2 ×
16.00 g/mole =
32.00 g/mole H 2 ×
1.01 g/mole = +
2.02 g/mole
61.00 g/mole
1 mole of Al(OH)3 molecules would have a mass of g

53. Percent Composition %

54. The percent by mass of each element present in a compound.
Percent Composition
The percent by mass of each element present in a compound.
Example: H2O → 1 mole = grams of H2O
2 moles of H: 2 x = grams
1 mole of O: 1 x 16 = 16 grams
% of H → x 100% = 11.19% % of O → 16 x 100% = 88.81%

55. Example: KMnO4
Find the mass of each element: K → Mn → O (4) →

56. Example: C6H12O6
First, find the masses of each element: C (6) → H (12) → O (6) →

57. Using Molar Mass in Conversions

60. Example: Moles to grams
How many grams are in 1.25 moles of water? 1 H O 2 1
1.01 g/mole
16.00 g/mole × =
2.02 g/mole +
18.02 g/mole
1 mole H2O molecules = g

61. Example: Moles to grams
How many grams are in 1.25 moles of water? 2
1 mole H2O molecules = g
1.25 mol H2O
18.02
g H2O
= _______ g H2O
22.53 1
mol H2O

62. Example: Grams to moles
How many moles are in 25.5 grams of NaCl? 1 Na Cl 1
22.99 g/mole
35.45 g/mole × = +
58.44 g/mole
1 mole NaCl molecules = g

63. Example: Moles to grams
How many moles are in 25.5 grams of NaCl?
1 mole NaCl = g 2
25.5 g NaCl 1
mole NaCl
= _______ mole NaCl
0.44
58.44
g NaCl

64. Example: Grams to Molecules
How many molecules are in 25.5 grams NaCl? Think: what steps need to be taken? 1. Convert grams to moles 2. Convert moles to molecules

65. Example: Grams to Molecules
How many molecules are in 25.5 grams NaCl?
Example: Grams to Molecules 1 Na Cl 1
22.99 g/mole
35.45 g/mole × = +
58.44 g/mole
1 moles NaCl molecules = g
1 mol = 6.02×1023 molecules

66. Example: Grams to Molecules
How many molecules are in 25.5 grams NaCl?
Example: Grams to Molecules 2
1 moles NaCl molecules = g
1 mol = 6.02×1023 molecules
25.5 g NaCl 1
mol NaCl
6.02×1023
molecules NaCl
58.44
g NaCl 1
mol NaCl
= _________ molecules NaCl
2.63 × 1023

67. Example: Molecules to grams
How many grams is a sample
of 2.75 x 1024 molecules of SrCl2?
Think: what steps need to be taken?
1. Convert molecules to moles
2. Convert moles to grams

68. Example: Molecules to grams
How many grams is a sample of 2.75 x 1024 molecules of SrCl2?
Example: Molecules to grams 1 Sr Cl 1 2
87.62 g/mole
35.45 g/mole × =
70.90 g/mole +
g/mole
1 moles SrCl2 molecules = g
1 mol = 6.02×1023 molecules

69. Example: Molecules to Grams
How many grams is a sample of 2.75 x 1024 molecules of SrCl2?
Example: Molecules to Grams 2
1 moles SrCl2 molecules = g
2.75 × 1024 molecules
SrCl2 1
mol SrCl2
158.52
g SrCl2
6.02 × 1023
molecules
SrCl2 1
mol SrCl2
= _________ g SrCl2
7.24