1. Percent Composition, Empirical and Molecular Formulas Courtesy www.lab-initio.com

2. Calculating Percentage Composition (a review) When you are asked to calculate the percentage composition, you are finding out the percentage by mass of an element.

3. Calculating Percentage Composition (a review) When you are asked to calculate the percentage composition, you are finding out the percentage by mass of an element. The percentage composition does not tell us the ratio by which the atoms combine.

4. Calculating Percentage Composition (a review) When you are asked to calculate the percentage composition, you are finding out the percentage by mass of an element. The percentage composition does not tell us the ratio by which the atoms combine. (doesn’t give us the subscripts for the chemical formula)

5. Calculating Percentage Composition (a review) Lets review how to calculate a percentage.

6. Calculating Percentage Composition (a review) Lets review how to calculate a percentage. Jackson goes to a school that has 258 total students. If 164 of the students were boys, what percentage of the student body is made up of boys?

7. Calculating Percentage Composition (a review) Lets review how to calculate a percentage. Jackson goes to a school that has 258 total students. If 164 of the students were boys, what percentage of the student body is made up of boys?

8. Calculating Percentage Composition (a review) Lets review how to calculate a percentage. Jackson goes to a school that has 258 total students. If 164 of the students were boys, what percentage of the student body is made up of boys?

9. Calculating Percentage Composition (a review) So generally:

10. Calculating Percentage Composition (a review) So generally:

11. Calculating Percentage Composition Calculate the percentage composition of magnesium carbonate, MgCO 3.

12. Calculating Percentage Composition Calculate the percentage composition of magnesium carbonate, MgCO 3. Step One: Determine the molar mass of the substance.

13. Calculating Percentage Composition Calculate the percentage composition of magnesium carbonate, MgCO 3. Step One: Determine the molar mass of the substance. Step Two: To find the percentage composition of each element, use the total mass of that element (from step one) in the equation below.

14. Calculating Percentage Composition Calculate the percentage composition of magnesium carbonate, MgCO 3. Step One: Determine the molar mass of the substance. Step Two: To find the percentage composition of each element, use the total mass of that element (from step one) in the equation below.

15. Calculating Percentage Composition Calculate the percentage composition of magnesium carbonate, MgCO 3. Step One: Determine the molar mass of the substance. Step Two: To find the percentage composition of each element, use the total mass of that element (from step one) in the equation below. Step Four: Check your calculations by adding up the percentages of all elements. They should add up to 100%

16. Calculating Percentage Composition Calculate the percentage composition of magnesium carbonate, MgCO 3.

17. Calculating Percentage Composition Calculate the percentage composition of magnesium carbonate, MgCO 3. Molar mass of magnesium carbonate: 1(Mg) + 1(C) + 3(O) 24.31 g + 12.01 g + 3(16.00 g) = 84.32 g

18. Calculating Percentage Composition Calculate the percentage composition of magnesium carbonate, MgCO 3. Molar mass of magnesium carbonate: 1(Mg) + 1(C) + 3(O) 24.31 g + 12.01 g + 3(16.00 g) = 84.32 g

19. Calculating Percentage Composition Calculate the percentage composition of magnesium carbonate, MgCO 3. Molar mass of magnesium carbonate: 1(Mg) + 1(C) + 3(O) 24.31 g + 12.01 g + 3(16.00 g) = 84.32 g

20. Calculating Percentage Composition Calculate the percentage composition of magnesium carbonate, MgCO 3. Molar mass of magnesium carbonate: 1(Mg) + 1(C) + 3(O) 24.31 g + 12.01 g + 3(16.00 g) = 84.32 g

21. Calculating Percentage Composition Calculate the percentage composition of magnesium carbonate, MgCO 3. Molar mass of magnesium carbonate: 1(Mg) + 1(C) + 3(O) 24.31 g + 12.01 g + 3(16.00 g) = 84.32 g 100.00%

22. Formulas Empirical formula: the lowest whole number ratio of atoms in a compound.

23. Formulas Empirical formula: the lowest whole number ratio of atoms in a compound. Molecular formula: the true number of atoms of each element in the formula of a compound.

24. Formulas  molecular formula = (empirical formula) n Empirical formula: the lowest whole number ratio of atoms in a compound. Molecular formula: the true number of atoms of each element in the formula of a compound.

25. Formulas  molecular formula = (empirical formula) n  molecular formula = C 6 H 6 = (CH) 6 Empirical formula: the lowest whole number ratio of atoms in a compound. Molecular formula: the true number of atoms of each element in the formula of a compound.

26. Formulas  molecular formula = (empirical formula) n  molecular formula = C 6 H 6 = (CH) 6  empirical formula = CH Empirical formula: the lowest whole number ratio of atoms in a compound. Molecular formula: the true number of atoms of each element in the formula of a compound.

27. Formulas (continued) Formulas for ionic compounds are ALWAYS empirical (lowest whole number ratio).

28. Formulas (continued) Formulas for ionic compounds are ALWAYS empirical (lowest whole number ratio). Examples: NaCl

29. Formulas (continued) Formulas for ionic compounds are ALWAYS empirical (lowest whole number ratio). Examples: NaCl MgCl 2

30. Formulas (continued) Formulas for ionic compounds are ALWAYS empirical (lowest whole number ratio). Examples: NaCl MgCl 2 Al 2 (SO 4 ) 3

31. Formulas (continued) Formulas for ionic compounds are ALWAYS empirical (lowest whole number ratio). Examples: NaCl MgCl 2 Al 2 (SO 4 ) 3 K 2 CO 3

32. Formulas (continued) Formulas for molecular compounds MIGHT be empirical (lowest whole number ratio).

33. Formulas (continued) Formulas for molecular compounds MIGHT be empirical (lowest whole number ratio). Molecular: H2OH2O

34. Formulas (continued) Formulas for molecular compounds MIGHT be empirical (lowest whole number ratio). Molecular: H2OH2O Empirical: H2OH2O

35. Formulas (continued) Formulas for molecular compounds MIGHT be empirical (lowest whole number ratio). Molecular: H2OH2O C 6 H 12 O 6 Empirical: H2OH2O

36. Formulas (continued) Formulas for molecular compounds MIGHT be empirical (lowest whole number ratio). Molecular: H2OH2O C 6 H 12 O 6 Empirical: H2OH2O CH 2 O

37. Formulas (continued) Formulas for molecular compounds MIGHT be empirical (lowest whole number ratio). Molecular: H2OH2O C 6 H 12 O 6 C 12 H 22 O 11 Empirical: H2OH2O CH 2 O

38. Formulas (continued) Formulas for molecular compounds MIGHT be empirical (lowest whole number ratio). Molecular: H2OH2O C 6 H 12 O 6 C 12 H 22 O 11 Empirical: H2OH2O CH 2 OC 12 H 22 O 11

39. Empirical Formula Determination 1.Base calculation on 100 grams of compound. Determine moles of each element in 100 grams of compound.

40. Empirical Formula Determination 1.Base calculation on 100 grams of compound. Determine moles of each element in 100 grams of compound. 2.Divide each value of moles by the smallest of the values.

41. Empirical Formula Determination 1.Base calculation on 100 grams of compound. Determine moles of each element in 100 grams of compound. 2.Divide each value of moles by the smallest of the values. 3.Multiply each number by an integer to obtain all whole numbers.

42. Empirical Formula Determination Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula of adipic acid?

43. Empirical Formula Determination Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula of adipic acid? 1.Treat % as mass, and convert grams to moles of that element.

44. Empirical Formula Determination Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula of adipic acid? 1.Treat % as mass, and convert grams to moles of that element.

45. Empirical Formula Determination Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula of adipic acid? 1.Treat % as mass, and convert grams to moles of that element.

46. Empirical Formula Determination Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula of adipic acid? 1.Treat % as mass, and convert grams to moles of that element.

47. Empirical Formula Determination 2. Divide each value of moles by the smallest of the values.

48. Empirical Formula Determination 2. Divide each value of moles by the smallest of the values. Carbon:

49. Empirical Formula Determination 2. Divide each value of moles by the smallest of the values. Carbon: Hydrogen:

50. Empirical Formula Determination 2. Divide each value of moles by the smallest of the values. Carbon: Hydrogen: Oxygen:

51. Empirical Formula Determination 3. Multiply each number by an integer to obtain all whole numbers.

52. Empirical Formula Determination 3. Multiply each number by an integer to obtain all whole numbers. Carbon: 1.50 x 2 3

53. Empirical Formula Determination 3. Multiply each number by an integer to obtain all whole numbers. Carbon: 1.50 Hydrogen: 2.50 x 2 35

54. Empirical Formula Determination 3. Multiply each number by an integer to obtain all whole numbers. Carbon: 1.50 Hydrogen: 2.50 Oxygen: 1.00 x 2 352

55. Empirical Formula Determination 3. Multiply each number by an integer to obtain all whole numbers. Carbon: 1.50 Hydrogen: 2.50 Oxygen: 1.00 x 2 352 Empirical formula: C3H5O2C3H5O2

56. Finding the Molecular Formula The empirical formula for adipic acid is C 3 H 5 O 2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid?

57. Finding the Molecular Formula The empirical formula for adipic acid is C 3 H 5 O 2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid? 1. Find the molar mass of C 3 H 5 O 2

58. Finding the Molecular Formula The empirical formula for adipic acid is C 3 H 5 O 2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid? 1. Find the molar mass of C 3 H 5 O 2 3(C) + 5(H) + 2(O) 3(C) + 5(H) + 2(O) 3(12.01 g) + 5(1.01g) + 2(16.00g) = 73.08 g

59. Finding the Molecular Formula The empirical formula for adipic acid is C 3 H 5 O 2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid? 1. Find the molar mass of C 3 H 5 O 2 3(C) + 5(H) + 2(O) 3(C) + 5(H) + 2(O) 3(12.01 g) + 5(1.01g) + 2(16.00g) = 73.08 g The mass of adipic acid based on the empirical formula 1 mole C 3 H 5 O 2 = 73.08 g

60. Finding the Molecular Formula The empirical formula for adipic acid is C 3 H 5 O 2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid?

61. Finding the Molecular Formula The empirical formula for adipic acid is C 3 H 5 O 2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid? 1 mole C 3 H 5 O 2 = 73.08 g

62. Finding the Molecular Formula The empirical formula for adipic acid is C 3 H 5 O 2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid? 2. Divide the molecular mass by the mass given by the emipirical formula. 1 mole C 3 H 5 O 2 = 73.08 g

63. Finding the Molecular Formula The empirical formula for adipic acid is C 3 H 5 O 2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid? 2. Divide the molecular mass by the mass given by the emipirical formula. 1 mole C 3 H 5 O 2 = 73.08 g

64. Finding the Molecular Formula The empirical formula for adipic acid is C 3 H 5 O 2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid? 3. Multiply the empirical formula by this number to get the molecular formula. (C 3 H 5 O 2 ) x 2 = C 6 H 10 O 4

65. Finding the Molecular Formula The empirical formula for adipic acid is C 3 H 5 O 2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid?

66. Finding the Molecular Formula The empirical formula for adipic acid is C 3 H 5 O 2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid?

67. Finding the Molecular Formula The empirical formula for adipic acid is C 3 H 5 O 2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid? 3. Multiply the empirical formula by this number to get the molecular formula.

68. Finding the Molecular Formula The empirical formula for adipic acid is C 3 H 5 O 2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid? 3. Multiply the empirical formula by this number to get the molecular formula. (C 3 H 5 O 2 ) x 2 =

69. Finding the Molecular Formula The empirical formula for adipic acid is C 3 H 5 O 2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid? 3. Multiply the empirical formula by this number to get the molecular formula. (C 3 H 5 O 2 ) x 2 = C 6 H 10 O 4