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Percent Composition, Empirical Formulas, Molecular Formulas
Week 22 Chemistry Percent Composition, Empirical Formulas, Molecular Formulas
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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
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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]
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Bubble Gum Lab
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Problem What percentage of Double Bubble Gum is composed of sugar?
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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%
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Lab Expectations Work in assigned groups
Raise your hand if you have a question No gum should be left on the desks
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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
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Bubble Gum Lab You each need One Piece of Gum and your Brain Good Luck!!! 15 Minutes
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Answer Key As Mr. Ghosh goes through the answers, highlight the ones you got wrong
C D B 12. B 13. B 14. A 15. C 16. A 17. C 18. A 19. A 20. B 21. C
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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%
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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
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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
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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]
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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
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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
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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
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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
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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
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Closing Explain the purpose of today’s lab
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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
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Agenda Warm Up [7 minutes] Notes/Examples [15 minutes]
Guided Practice [12 minutes] Independent Practice [15 minutes] Closing [3 Minutes]
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What is % Composition?? Percent by mass of each element in a compound
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What is % Composition?? % composition by mass= Mass of part Mass of Whole x 100%
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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?
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Example 2: What is the percent composition by mass of the elements in the compound, AgNO3?
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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
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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
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Guided Practice 2: What is the percent composition by mass of the elements in Mercury (II) Oxide? 92.6% Hg 7.4% O
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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
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Practice makes Perfect
Independent Practice Take some time to practice finding the % composition of the following compounds 85% Practice makes Perfect
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Closing How do you find the percent composition of an element in a compound?
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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
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Agenda Warm Up [7 minutes] Notes/Examples [15 minutes]
Guided Practice [12 minutes] Independent Practice [15 minutes] Closing [3 Minutes]
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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
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Empirical Formulas Shows the lowest number ratio of atoms in a compound empirical formula of glucose = CH2O
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Example 1: What is the empirical formula for a chemical compound that is 79.8% C and 20.2% H?
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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.
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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
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Example 2: What is the empirical formula for a compound that is 81.7% Be and 18.3% H?
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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
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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
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Guided Practice 2: What is the Empirical Formula of a compound that is 88.2 % Oxygen and 11.8% Hydrogen by mass? H2O
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Guided Practice 3: What is the empirical formula of a compound that is made from 50% Cesium and 50% Iodine by mass? CsI
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Practice makes Perfect
Independent Practice 85% Practice makes Perfect
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Closing What is the empirical formula?
How do you compose the empirical formula?
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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
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Agenda Warm Up [7 minutes] Notes/Examples [15 minutes]
Guided Practice [12 minutes] Independent Practice [15 minutes] Closing [3 Minutes]
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More Empirical Formulas!!
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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?
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Example 1: What is the empirical formula for a chemical compound that is 49.1% Be and 50.9% N?
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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
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Table of Common Decimals/Fractions
Mole Ratio Multiply all mole ratios by
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Multiply all mole ratios by
Table of Common Decimals/Fractions Mole Ratio Multiply all mole ratios by X.5
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Table of Common Decimals/Fractions
Mole Ratio Multiply all mole ratios by X.5 2
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Table of Common Decimals/Fractions
Mole Ratio Multiply all mole ratios by X.5 2 X.33
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Table of Common Decimals/Fractions
Mole Ratio Multiply all mole ratios by X.5 2 X.33 3
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Table of Common Decimals/Fractions
Mole Ratio Multiply all mole ratios by X.5 2 X.33 3 X.66
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Table of Common Decimals/Fractions
Mole Ratio Multiply all mole ratios by X.5 2 X.33 3 X.66
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Table of Common Decimals/Fractions
Mole Ratio Multiply all mole ratios by X.5 2 X.33 3 X.66 X.75
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Table of Common Decimals/Fractions
Mole Ratio Multiply all mole ratios by X.5 2 X.33 3 X.66 X.75 4
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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
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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
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Example 1: What is the empirical formula for a chemical compound that is 49.1% Be and 50.9% N?
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Example 2: What is the empirical formula of a compound that is 25.9% Nitrogen and % Oxygen by mass?
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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
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Guided Practice 1: What is the Empirical Formula of a compound that is 25.9% P and 74.1% Cl? P2Cl5
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Guided Practice 2: What is the Empirical Formula of a compound that is 17.4% Nitrogen and 82.6% Fluorine? N2F7
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Guided Practice 3: What is the Empirical Formula of a compound that is made from 35.9% Aluminum and 64.1% Sulfur? Al2S3
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Practice makes Perfect
Independent Practice 85% Practice makes Perfect
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Closing What is the empirical formula?
How do you compose the empirical formula?
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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
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Agenda Warm Up [6 minutes] Notes/Examples [11 minutes]
Guided Practice [9 minutes] Quiz [20 minutes] Closing [1 Minute]
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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
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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
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Is CH2 an empirical or a molecular formula?
Check Point #1 Is CH2 an empirical or a molecular formula? Empirical
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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)
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Example 1: What is the molecular formula if the empirical formula is CH4O and the mass of the whole molecule is 96 g/mol?
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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
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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
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Example 2: Compose the molecular formula of the compound whose molar mass is g/mol and empirical formula is CH4N.
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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
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Guided Practice 1: Compose the molecular formula of the compound whose molar mass is 90 g/mol and empirical formula is CH2O. C3H6O3
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Guided Practice 2: Compose the molecular formula of the compound whose molar mass is 62 g/mol and empirical formula is CH3O. C2H6O2
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Practice makes Perfect
Independent Practice 85% Practice makes Perfect
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Material Covered on Quiz
Mole Calculations (1 and 2 step) Percent Composition Empirical Formulas
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Goal To demonstrate mastery, we are shooting for 85%
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Check Point What is your goal for this quiz? 85%
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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
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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
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Good Luck!!
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Closing How was your quiz?
What topics do you feel you still need review on?
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