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# Empirical and Molecular

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### Empirical and Molecular

1. 1. Chapter Eight Part II
2. 2. <ul><li>Obtain one piece of gum, and find its mass in the wrapper. </li></ul><ul><li>Keep the wrapper for later and start chewing. We are experimenting. </li></ul>
3. 3. Percents <ul><li>If you have 7 green cars, 8 blue cars, and 4 red cars, what percentage is green? </li></ul>
4. 4. Percents % = part whole x 100
5. 5. Percents <ul><li>The mass of a mini Hershey Bar is 6.5 grams and the mass of a mini Mr. Goodbar is 8.3 grams. If you have a basket with 5 Hershey bars and 3 Mr. Goodbars, what is the percent BY MASS of each? </li></ul>
6. 6. Percentage Composition <ul><li>Percent Composition is finding the percent by mass of each element in a compound using the periodic table. </li></ul>
7. 7. Percentage Composition <ul><li>What is the percent by mass of each element in FeSO 4 ? </li></ul>
8. 8. Percentage Composition <ul><li>What is the percent by mass of each element in Mg 3 (PO 4 ) 2 ? </li></ul>
9. 9. Percentage Composition <ul><li>What is the percent by mass of carbon in sucrose, C 12 H 22 O 11 ? </li></ul>
10. 10. Percentage Composition <ul><li>An 8.20 gram piece of magnesium combines with 5.40 grams of oxygen to form a compound. </li></ul><ul><li>What is the percent composition of this compound? </li></ul>
11. 11. Review <ul><li>Find the percent of oxygen in each of the following: </li></ul><ul><li>Rb 2 O </li></ul><ul><li>Al(NO 3 ) 3 </li></ul>
12. 12. Percentage Composition <ul><li>How many grams of Ca are in 64.3 grams CaCl 2 ? </li></ul>
13. 13. You Try <ul><li>How many grams of Oxygen are in 19.2 grams Na 3 PO 4 ? </li></ul>Oxygen
14. 14. You try <ul><li>How many grams of oxygen are in 56.0 grams of each of the following: </li></ul><ul><li>Rb 2 O </li></ul><ul><li>Al(NO 3 ) 3 </li></ul>
15. 15. Finding a ratio <ul><li>If a school has 30 boys and 60 girls, what is the ratio of boys to girls? </li></ul>
16. 16. Finding a whole number ratio in its lowest terms <ul><li>If a school has 27 boys and 18 girls, what is the ratio of boys to girls? </li></ul>
17. 17. Finding a whole number ratio in its lowest terms <ul><li>If a school has 75 boys and 60 girls, what is the ratio of boys to girls? </li></ul>
18. 18. Finding a whole number ratio in its lowest terms <ul><li>A certain compound contains 4.14 moles of Mg and 2.76 moles of P. </li></ul><ul><li>Find the mole ratio between Mg and P. </li></ul><ul><li>Write the formula. </li></ul>
19. 19. Empirical Formula <ul><li>An Empirical formula gives the lowest whole number MOLE ratio between the atoms in a compound. </li></ul>
20. 20. The Math <ul><li>A compound contains 0.900 grams of calcium and 1.60 grams of chlorine. </li></ul><ul><li>Find its empirical formula. </li></ul>
21. 21. The Math <ul><li>A compound is analyzed and found to consist of 36.0 % aluminum and 64.2 % sulfur. </li></ul><ul><li>Find its empirical formula. </li></ul>
22. 22. We Try <ul><li>Calculate the empirical formula of a compound that is 62.0 % C, 13.9 % H, and 24.1 % N. </li></ul>
23. 23. You Try <ul><li>What is the empirical formula of a compound that is 66.0 % Ca and 34.0 % P? </li></ul>
24. 24. You Try <ul><li>Benzoic Acid is used as a preservative, A 15.0 gram sample contains 10.32 grams of C, 0.743 grams of H, and 3.93 grams of O. Find the empirical formula. </li></ul>
25. 25. Molecular Formula <ul><li>A Molecular formula gives the actual ratio between the atoms in a compound. </li></ul><ul><li>For Ionic compounds, the empirical and molecular formulas are the same. </li></ul>
26. 26. Molecular Formula <ul><li>For molecular compounds, the molecular formula is a multiple of the empirical. </li></ul><ul><li>Example: </li></ul><ul><li>C 6 H 6 is benzene. What is benzene’s empirical formula? </li></ul>
27. 27. Molecular Formula <ul><li>Example: </li></ul><ul><li>C 2 H 6 is ethane. What is ethane’s empirical formula? </li></ul>
28. 28. The Math <ul><li>A compound contains 31.10 grams of carbon and 7.872 grams of hydrogen. </li></ul><ul><li>Find its empirical formula. </li></ul>
29. 29. The Math <ul><li>What is the same compound’s molecular formula if its molar mass = 90.18 g/mol? </li></ul>
30. 30. Molecular formula <ul><li>What is the molecular formula of dichloroacetic acid, if the empirical formula is CHOCl, and its molar mass is 129 g/mol. </li></ul>
31. 31. Molecular formula <ul><li>Vitamin C is ascorbic acid. It has a percentage composition of 40.9 % carbon, 4.58 % hydrogen, and 54.5 % oxygen with a molecular mass of 176.1 u. </li></ul><ul><li>Find its empirical and molecular formulae. </li></ul>
32. 32. Review Molecular formula <ul><li>Aspirin, acetylsalicylic acid, contains 60.0 % carbon, 4.48 % hydrogen, and 35.5 % oxygen with a molecular mass of 180 u. </li></ul><ul><li>Find its empirical and molecular formulae. </li></ul>
33. 33. Molecular formula <ul><li>Find its empirical and molecular formulae, if a compound contains 40.0 % carbon, 6.73 % hydrogen, and 53.3 % oxygen with a mass of 240 g/mol. </li></ul>
34. 34. Hydrates <ul><li>Hydrates are compounds with water molecules trapped in their crystal structure. </li></ul><ul><li>The water is weakly bonded and can be removed by heating the substance. </li></ul>
35. 35. Hydrates <ul><li>Example: </li></ul><ul><li>Li 2 SO 4 * 2 H 2 O </li></ul><ul><li>This formula tells you that 1 mole of lithium sulfate is bonded to 2 moles of water. </li></ul>
36. 36. Hydrates <ul><li>Example: </li></ul><ul><li>MgCO 3 * 7 H 2 O </li></ul><ul><li>This formula tells you that 1 mole of magnesium carbonate is bonded to 7 moles of water. </li></ul>
37. 37. Hydrates <ul><li>Example: </li></ul><ul><li>MgSO 3 * 6 H 2 O </li></ul><ul><li>This formula tells you that 1 mole of magnesium sulfite is bonded to 6 moles of water. </li></ul>
38. 38. Hydrates <ul><li>Notice the mole ratio is shown as a coefficient and the compound gets the 1. </li></ul><ul><li>General form: </li></ul><ul><li>any compound * __ H 2 O </li></ul>
39. 39. We try <ul><li>0.391 grams of Li 2 SiF 6 is found to contain 0.0903 grams of water. </li></ul><ul><li>Find the formula for the hydrate </li></ul>
40. 40. We try <ul><li>A compound is analyzed and found to contain 86.7 % Mo 2 S 5 and 13.3 % water. </li></ul><ul><li>Find the formula for the hydrate </li></ul>
41. 41. You try <ul><li>A particular hydrate contains 89.2 % BaBr 2 . </li></ul><ul><li>Find the formula for the hydrate. </li></ul>
42. 42. Quiz Review <ul><li>A particular hydrate of MgSO 4 contains 51.14 % water. </li></ul><ul><li>Find the formula for the hydrate. </li></ul>
43. 43. Quiz Review <ul><li>Find the percentage of water in the hydrate, Na 2 CO 3 * 10 H 2 O. </li></ul>
44. 44. Quiz Review <ul><li>Find the percentage of oxygen in P 2 O 5 . </li></ul><ul><li>How many grams of oxygen are in 25.5 grams of P 2 O 5 ? </li></ul>
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