1. Percent Composition, Empirical Formulas, Molecular Formulas
Week 22 Chemistry
Percent Composition, Empirical Formulas, Molecular Formulas

2. Record your Learning Target
Warm Up: 3 Minutes
Record your Learning Target
Stay in your own seat
You should be working SILENTLY
A certain bag of M&M’s has 8 blue candies, 7 red candies, 4 green candies, and 6 yellow candies. What percentage of the bag is blue M&M’s?
Do the warm up in OneNote

3. Agenda Warm Up [6 minutes] Pre-Lab/Expectations [7 minutes]
Bubble Gum Lab [18 minutes]
Answer Key [ 4 minutes]
Modeling Tracking [5 minutes]
You Track [10 minutes]
Closing [3 Minutes]

4. Bubble Gum Lab

5. Problem
What percentage of Double Bubble Gum is composed of sugar?

6. Pre-Lab Question
According to the nutritional manufacturer, each piece of gum has a mass of 6g with 5g of sugar. Using this information, what percent of the gum is sugar by mass?
% 𝑆𝑢𝑔𝑎𝑟= 𝑀𝑎𝑠𝑠 𝑜𝑓 𝑆𝑢𝑔𝑎𝑟 𝑀𝑎𝑠𝑠 𝑜𝑓 𝐺𝑢𝑚 𝑥 100%

7. Lab Expectations Work in assigned groups
Raise your hand if you have a question
No gum should be left on the desks

8. General information: How to do the lab
Find the mass of your piece of gum before chewing (include the wrapper)
Chew your gum for ~5 minutes
Find the mass of your piece of gum after chewing
Gum should be placed in wrapper before putting it on mass balance
Complete analysis and post-lab questions

9. Bubble Gum Lab
You each need One Piece of Gum and your Brain
Good Luck!!!
15 Minutes

10. Answer Key As Mr. Ghosh goes through the answers, highlight the ones you got wrongC D B
12. B 13. B 14. A 15. C 16. A 17. C 18. A 19. A 20. B 21. C

11. Class Averages (and Top Scores)
Period
Top Score
Class Average 1
95%
60% 3
100%
70% 4
90%
79% 5
71% 6
66% 7
64%

12. What does Tracking Look Like?
Objectives
Questions on the Exam
Your Points
Total Points
Percent Mastery
Bar Graph
Mastery
85%
 or 
Chem.7C
Lewis Dot Structures

13. What does Tracking Look Like?
Objectives
Questions on the Exam
Your Points
Total Points
Percent Mastery
Bar Graph
Mastery
85%
 or 
Chem.7C
Lewis Dot Structures
1-5

14. What does Tracking Look Like?
Objectives
Questions on the Exam
Your Points
Total Points
Percent Mastery
Bar Graph
Mastery
85%
 or 
Chem.7C
Lewis Dot Structures
1-5
???
[3 if you got 3 out of 5 correct]

15. What does Tracking Look Like?
Objectives
Questions on the Exam
Your Points
Total Points
Percent Mastery
Bar Graph
Mastery
85%
 or 
Chem.7C
Lewis Dot Structures
1-5
???
[3 if you got 3 out of 5 correct] 5

16. What does Tracking Look Like?
Objectives
Questions on the Exam
Your Points
Total Points
Percent Mastery
Bar Graph
Mastery
85%
 or 
Chem.7C
Lewis Dot Structures
1-5
???
[3 if you got 3 out of 5 correct] 5
Your points x100
Total points

17. Cathy received 1 point out of 4 possible points
Cathy received 1 point out of 4 possible points. What is her percent mastery?
Percent Mastery
25%
Your points x100
Total points

18. What does Tracking Look Like?
Objectives
Questions on the Exam
Your Points
Total Points
Percent Mastery
Bar Graph
Mastery
85%
 or 
Chem.7C
Lewis Dot Structures
1-5
???
[3 if you got 3 out of 5 correct] 5
Your points x100
Total points
Shade in your % mastery

19. Your Turn Go to shschem.weebly.com (our class website)
Hover over my page:
Mr. Ghosh  Homework Assignments  ESL (or regular) Chemistry
Under Homework Assignments, there is a new one labeled “Unit 5 Tracking”
Download (and save) this and fill it out

20. Closing
Explain the purpose of today’s lab

21. Warm Up: 4 Minutes Stay in your own seat
You should be working SILENTLY
Log into your computer
Go to m.socrative.com
Enter room number:
Finish all questions
When you are finished, check your grades on PS Connect

22. Agenda Warm Up [7 minutes] Notes/Examples [15 minutes]
Guided Practice [12 minutes]
Independent Practice [15 minutes]
Closing [3 Minutes]

24. What is % Composition??
Percent by mass of each
element in a compound

25. What is % Composition??
% composition by mass= Mass of part Mass of Whole x 100%

26. Example 1:
A compound contains 2.0g of sodium, 3.5g of oxygen, and 0.5 g of hydrogen. What is the percent composition of this compound?

27. Example 2:
What is the percent composition by mass of the elements in the compound, AgNO3?

28. Guided Practice Teacher: Students:
1. Will show the problem on the board
Students:
Take 24 seconds to identify your given and unknown.
Take 46 seconds to speak with your shoulder partner about the problem
Be ready to share when Mr. Ghosh says SWAG

29. Guided Practice 1:
9.03 g Magnesium combines completely with 3.48 g Nitrogen to form a compound. What is the percent composition of Nitrogen in this compound?
27.82 % N

30. Guided Practice 2:
What is the percent composition by mass of the elements in Mercury (II) Oxide?
92.6% Hg
7.4% O

31. What is the percent composition by mass of the elements in K2CO3?
Guided Practice 3:
What is the percent composition by mass of the elements in K2CO3?
56.6% K
8.7% C
34.7% O

32. Practice makes Perfect
Independent Practice
Take some time to practice finding the % composition of the following compounds
85%
Practice makes Perfect

33. Closing
How do you find the percent composition of an element in a compound?

34. Write the Learning Target
Warm Up: 4 Minutes
Write the Learning Target
Stay in your own seat
You should be working SILENTLY
Log into your computer
Go to m.socrative.com
Enter room number:
Finish all questions
When you are finished, check your grades on PS Connect

35. Agenda Warm Up [7 minutes] Notes/Examples [15 minutes]
Guided Practice [12 minutes]
Independent Practice [15 minutes]
Closing [3 Minutes]

36. Percent Composition: CH3 79.8% C, 20.2% H Goal For Today
Student Given:
Student Answer:
Percent Composition:
79.8% C, 20.2% H
CH3

37. Empirical Formulas
Shows the lowest number ratio of atoms in a compound
empirical formula of glucose = CH2O

38. Example 1:
What is the empirical formula for a chemical compound that is 79.8% C and 20.2% H?

39. 79.8% C and 20.2% H How to Compose the Empirical Formula?
Step 1: Convert Percent to Grams Step 2: Convert Grams to Moles by dividing grams by the atomic mass of each element.

40. 79.8% C and 20.2% H How to Compose the Empirical Formula?
Step 3:Divide both molar quantities by the smallest mole quantity to determine the subscript for each element in the formula

41. Example 2:
What is the empirical formula for a compound that is 81.7% Be and 18.3% H?

42. Guided Practice Teacher: Students:
1. Will show the problem on the board
Students:
Take 22 seconds to identify the elements involved.
Take 68 seconds to solve the problem with your shoulder partner
Be ready to share when Mr. Ghosh says SWAG

43. Guided Practice 1:
What is the Empirical Formula of a compound that is 67.6% Hg, 10.8% S, and 21.6 % O by mass?
HgSO4

44. Guided Practice 2:
What is the Empirical Formula of a compound that is 88.2 % Oxygen and 11.8% Hydrogen by mass?
H2O

45. Guided Practice 3:
What is the empirical formula of a compound that is made from 50% Cesium and 50% Iodine by mass?
CsI

46. Practice makes Perfect
Independent Practice
85%
Practice makes Perfect

47. Closing What is the empirical formula?
How do you compose the empirical formula?

48. Warm Up: 4 Minutes Stay in your own seat
You should be working SILENTLY
Log into your computer
Go to m.socrative.com
Enter room number:
Finish all questions
When you are finished, check your grades on PS Connect

49. Agenda Warm Up [7 minutes] Notes/Examples [15 minutes]
Guided Practice [12 minutes]
Independent Practice [15 minutes]
Closing [3 Minutes]

50. More Empirical Formulas!!

51. Writing Empirical Formulas
Most of the time, our mole ratios come out close to a whole number (~.9, ~.1):
Ratio from Calculator
What we assume
Examples:
1.992 2 16
4.962 5
6.071 6
But what if our mole ratio comes out to something like ? What do we do then?

52. Example 1:
What is the empirical formula for a chemical compound that is 49.1% Be and 50.9% N?

53. Common Decimals/Fractions
When we find a mole ratio that ends up close to a common decimal/fraction:
X.5
X.75
X.33
X.25
X.66
We must multiply these ratio values by a specific number

54. Table of Common Decimals/Fractions
Mole Ratio
Multiply all mole ratios by

55. Multiply all mole ratios by
Table of Common Decimals/Fractions
Mole Ratio
Multiply all mole ratios by
X.5

56. Table of Common Decimals/Fractions
Mole Ratio
Multiply all mole ratios by
X.5 2

57. Table of Common Decimals/Fractions
Mole Ratio
Multiply all mole ratios by
X.5 2
X.33

58. Table of Common Decimals/Fractions
Mole Ratio
Multiply all mole ratios by
X.5 2
X.33 3

59. Table of Common Decimals/Fractions
Mole Ratio
Multiply all mole ratios by
X.5 2
X.33 3
X.66

60. Table of Common Decimals/Fractions
Mole Ratio
Multiply all mole ratios by
X.5 2
X.33 3
X.66

61. Table of Common Decimals/Fractions
Mole Ratio
Multiply all mole ratios by
X.5 2
X.33 3
X.66
X.75

62. Table of Common Decimals/Fractions
Mole Ratio
Multiply all mole ratios by
X.5 2
X.33 3
X.66
X.75 4

63. Table of Common Decimals/Fractions
Mole Ratio
Multiply all mole ratios by
X.5 2
X.33 3
X.66
X.75 4
X.25

64. Table of Common Decimals/Fractions
Mole Ratio
Multiply all mole ratios by
X.5 2
X.33 3
X.66
X.75 4
X.25

65. Example 1:
What is the empirical formula for a chemical compound that is 49.1% Be and 50.9% N?

66. Example 2:
What is the empirical formula of a compound that is 25.9% Nitrogen and % Oxygen by mass?

67. Guided Practice Teacher: Students:
1. Will show the problem on the board
Students:
Take 22 seconds to identify the elements involved.
Take 68 seconds to solve the problem with your shoulder partner
Be ready to share when Mr. Ghosh says SWAG

68. Guided Practice 1:
What is the Empirical Formula of a compound that is 25.9% P and 74.1% Cl?
P2Cl5

69. Guided Practice 2:
What is the Empirical Formula of a compound that is 17.4% Nitrogen and 82.6% Fluorine?
N2F7

70. Guided Practice 3:
What is the Empirical Formula of a compound that is made from 35.9% Aluminum and 64.1% Sulfur?
Al2S3

71. Practice makes Perfect
Independent Practice
85%
Practice makes Perfect

72. Closing What is the empirical formula?
How do you compose the empirical formula?

73. Write the Learning Target
Warm Up: 4 Minutes
Write the Learning Target
Stay in your own seat
You should be working SILENTLY
Log into your computer
Go to m.socrative.com
Enter room number:
Finish all questions
When you are finished, check your grades on PS Connect

74. Agenda Warm Up [6 minutes] Notes/Examples [11 minutes]
Guided Practice [9 minutes]
Quiz [20 minutes]
Closing [1 Minute]

75. Empirical Formula: CH4O Molar Mass of Molecular Formula: 96 g/mol
Goal For Today
Student Given:
Student Answer:
Empirical Formula: CH4O Molar Mass of Molecular Formula: 96 g/mol
Molecular Formula:
C3H12O3

76. Molecular formula of glucose = C6H12O6
Molecular Formulas
Shows exactly how many of each atom is in a compound (unsimplified formula)
Molecular formula of glucose = C6H12O6

77. Is CH2 an empirical or a molecular formula?
Check Point #1
Is CH2 an empirical or a molecular formula?
Empirical

78. Molecular Is S3O6 an empirical or a molecular formula?
Check Point #2
Is S3O6 an empirical or a molecular formula?
Molecular
(Empirical Formula is SO2)

79. Example 1:
What is the molecular formula if the empirical formula is CH4O and the mass of the whole molecule is 96 g/mol?

80. Empirical Formula: CH4O Mass of Molecular Formula: 96 g/mol
How to Compose the Molecular Formula?
Step 1: Find the Mass of the Empirical Formula Step 2: Divide the mass of the Molecular Formula by the mass of the Empirical Formula
Empirical Formula: CH4O Mass of Molecular Formula: 96 g/mol

81. Empirical Formula: CH4O Mass of Molecular Formula: 96 g/mol
How to Compose the Molecular Formula?
Step 3: Multiply the subscripts in the empirical formula by the answer from step 2.
Empirical Formula: CH4O Mass of Molecular Formula: 96 g/mol

82. Example 2:
Compose the molecular formula of the compound whose molar mass is g/mol and empirical formula is CH4N.

83. Guided Practice Teacher: Students:
1. Will show the problem on the board
Students:
Take 22 seconds to identify the elements involved.
Take 68 seconds to solve the problem with your shoulder partner
Be ready to share when Mr. Ghosh says SWAG

84. Guided Practice 1:
Compose the molecular formula of the compound whose molar mass is 90 g/mol and empirical formula is CH2O.
C3H6O3

85. Guided Practice 2:
Compose the molecular formula of the compound whose molar mass is 62 g/mol and empirical formula is CH3O.
C2H6O2

86. Practice makes Perfect
Independent Practice
85%
Practice makes Perfect

87. Material Covered on Quiz
Mole Calculations (1 and 2 step)
Percent Composition
Empirical Formulas

88. Goal
To demonstrate mastery, we are shooting for
85%

89. Check Point
What is your goal for this quiz?
85%

90. Periodic Table is provided to you
Expectations for Quiz
Clear your desk of everything except a....
Writing Utensil
Calculator
Periodic Table is provided to you

91. Expectations Students will keep eyes on own paper
Cheating will result in an automatic ZERO
Students will remain SILENT for the duration of the quiz

92. Good Luck!!

93. Closing How was your quiz?
What topics do you feel you still need review on?