1. Empirical and Molecular Formulas

2. Objective: Objective: – Today I will be able to: Calculate an empirical formula from experimental data Calculate an empirical formula from experimental data Derive a molecular formula from experimental data Derive a molecular formula from experimental data Apply conversion factors to converting between mass, volume, and particles Apply conversion factors to converting between mass, volume, and particles Evaluation/Assessment: Evaluation/Assessment: – Informal Assessment – Monitoring student interactions as they complete the practice – Formal Assessment – Analyzing student responses to the empirical/molecular formula practice and stoichiometry practice Common Core Connection Common Core Connection – Make sense of problem and persevere in solving them – Look for and express regularity in repeated reasoning – Attend to precision – Use appropriate tools strategically

3. Lesson Sequence Evaluate: Warm – Up Evaluate: Warm – Up Evaluate: Review HW Evaluate: Review HW Explain: Empirical and Molecular Formula Notes Explain: Empirical and Molecular Formula Notes Elaborate: Empirical and Molecular Formula Practice Elaborate: Empirical and Molecular Formula Practice Elaborate: Mixed Stoichiometry Practice Elaborate: Mixed Stoichiometry Practice Evaluate: Exit Ticket Evaluate: Exit Ticket

4. Warm - Up What is the percentage of Ca in Ca 3 (PO 4 ) 2 ? What is the percentage of Ca in Ca 3 (PO 4 ) 2 ?

5. Objective Today I will be able to: Today I will be able to: – Calculate the percent composition of elements in a compound – Calculate an empirical formula from experimental data – Derive a molecular formula from experimental data

6. Homework Work on Mole Project Due March 7 Work on Mole Project Due March 7 – Sewing help session after school February 27 Enjoy your weekend Enjoy your weekend Quiz on Mole Calculations/ Percent Composition Next Wednesday Quiz on Mole Calculations/ Percent Composition Next Wednesday

7. Agenda Warm-Up Warm-Up Review HW Review HW Empirical and Molecular Formula Notes Empirical and Molecular Formula Notes Empircal and Molecular Formula Practice Empircal and Molecular Formula Practice Mixed Stoichiometry Practce Mixed Stoichiometry Practce Exit Ticket Exit Ticket

8. Review HW What questions do you have about the HW?

9. Empirical and Molecular Formula Notes

10. Empirical Formula

11. A formula that gives the simplest whole number ratio of atoms in a compound A formula that gives the simplest whole number ratio of atoms in a compound Example: The empirical formula for hydrogen peroxide is HO (the actual formula is H 2 O 2 ). This is not the actual formula; it tells you the ratio of hydrogen to oxygen is 1:1 Example: The empirical formula for hydrogen peroxide is HO (the actual formula is H 2 O 2 ). This is not the actual formula; it tells you the ratio of hydrogen to oxygen is 1:1

12. Empirical Formula A compound was analyzed and found to contain 13.5 g of Ca, 10.8 g of O, and.675 g of H. What is the empirical formula? A compound was analyzed and found to contain 13.5 g of Ca, 10.8 g of O, and.675 g of H. What is the empirical formula?

13. Empirical Formula Step 1: Find the mole amounts of each element Step 1: Find the mole amounts of each element 13.5 g Ca 1 1 mol 40 g Ca 10.8 g O 1 1 mol 16 g O.675 g H 1 1 mol 1 g H x x x= = =.337 mol Ca.675 mol O.675 mol H

14. Empirical Formula Step 2: Divide each mole value by the smallest number of moles Step 2: Divide each mole value by the smallest number of moles 13.5 g Ca 1 1 mol 40 g Ca 10.8 g O 1 1 mol 16 g O.675 g H 1 1 mol 1 g H x x x= = =.337 mol Ca.337 mol.675 mol O.337 mol.675 mol H.337 mol = = = 1 2 2

15. Empirical Formula Step 3: Determine the Empirical Formula Step 3: Determine the Empirical Formula Ca 1 O 2 H 2 or… Ca 1 O 2 H 2 or… Ca(OH) 2 Ca(OH) 2

16. Empirical Formula Determine the empirical formula for a compound containing 1.203 g of Ca and 2.128 g of Cl Determine the empirical formula for a compound containing 1.203 g of Ca and 2.128 g of Cl 1.203 g Ca 1 2.128 g Cl 1 1 mol 40 g Ca 1 mol 35.4 g Cl x x = =.03008 mol Ca.06011 mol Cl ________ _________.03008 mol = = 1 2 CaCl 2

17. Empirical Formula Practice Complete the practice at your desk. Ask Ms. Ose for help if you have questions!

18. Molecular Formula

19. Is always a whole number multiple of the empirical formula Is always a whole number multiple of the empirical formula Ex: A 100.0 g sample of TNT is composed of 31.7 g carbon, 2.60 g hydrogen, 18.5 g nitrogen, and 42.3 g oxygen. (Its molar mass is 227 g/mol) Ex: A 100.0 g sample of TNT is composed of 31.7 g carbon, 2.60 g hydrogen, 18.5 g nitrogen, and 42.3 g oxygen. (Its molar mass is 227 g/mol)

20. Molecular Formula Step 1: Determine the empirical formula Step 1: Determine the empirical formula 31.7 g C 1 2.60 g H 1 1 mol 12 g C 1 mol 1 g H x x = = 2.64 mol C 2.60 mol H ________ _________ 1.32 mol = = 1 2 C 2 H 2 NO 2 18.5 g N 1 42.3 g O 1 x x 1 mol 14 g N 1 mol 16 g O = = _________ 1.32 mol N 2.64 mol O 1.32 mol = = 2 2

21. Molecular Formula Step 2: Determine the empirical formula molar mass Step 2: Determine the empirical formula molar mass C 2 H 2 NO 2 = 72 g/mol C 2 H 2 NO 2 = 72 g/mol

22. Molecular Formula Step 3: Divide the molar mass by the empirical formula molar mass Step 3: Divide the molar mass by the empirical formula molar mass 227 g/mol 72 g/mol = 3.15 or 3

23. Molecular Formula Step 4: Multiply the empirical formula by the ratio of the molar mass to the empirical formula Step 4: Multiply the empirical formula by the ratio of the molar mass to the empirical formula 3 (C 2 H 2 NO 2 ) = C 6 H 6 N 3 O 6 3 (C 2 H 2 NO 2 ) = C 6 H 6 N 3 O 6

24. Molecular Formula Practice Complete the Practice at your desk ask Ms. Ose for help if you have questions.

25. Mixed Stoichiometry Conversions Complete the practice at your desk. Whatever you do not finish will become your HW

26. Exit Ticket On a scale of 1 to 5, how comfortable are you with empirical and molecular formula calculations? On a scale of 1 to 5, how comfortable are you with empirical and molecular formula calculations?