1. Chapter 7 The Mole

2. Collection Terms 1 trio= 3 singers 1 six-pack Cola=6 cans Cola drink 1 dozen donuts=12 donuts 1 gross of pencils=144 pencils

3. A Moles of Particles Contains 6.02 x 10 23 particles 1 mole C = 6.02 x 10 23 C atoms 1 mole H 2 O = 6.02 x 10 23 H 2 O molecules 1 mole NaCl = 6.02 x 10 23 Na + ions and 6.02 x 10 23 Cl – ions

4. Examples of Moles Moles of elements 1 mole Mg = 6.02 x 10 23 Mg atoms 1 mole Au = 6.02 x 10 23 Au atoms Moles of compounds 1 mole NH 3 = 6.02 x 10 23 NH 3 molecules 1 mole C 9 H 8 O 4 = 6.02 x 10 23 aspirin molecules

5. Avogadro’s Number is 6.02 x 10 23 or, 1 mole 6.02 x 10 23 particles 1 mole or 1 mole 6.02 x 10 23 particles

6. Using Isotopic Abundances to determine the Average Atomic Mass of an Element

7. Atomic Mass Determination What is this number 35.453 for Cl?? The atomic mass - is an average based on the percents and masses of each of the isotopes of chlorine Chlorine consists of 75.77% chlorine-35 (mm = 34.968853 amu) and 24.23% chlorine-37 (36.965903 amu)

8. Atomic Mass Determination Chlorine consists of 75.77% chlorine-35 (mm = 34.968853 amu) and 24.23% chlorine-37 (36.965903 amu) 1: convert the percentage to a decimal: 0.7577 chlorine-350.2423 chlorine-37 2: 0.7577 x 34.968853 amu = 26.4958992 amu 0.2423 x 36.965903 amu = 8.9651 amu 35.4527 amu

9. Atomic Mass Determination Nitrogen consists of two naturally occurring isotopes 99.63% nitrogen-14 with a mass of 14.003 amu 0.37% nitrogen-15 with a mass of 15.000 amu What is the atomic mass of nitrogen?

10. Finding the Molar Masses of Elements and Compounds

11. Molar Mass of Elements remember these are atoms Number of grams in 1 mole of atoms Equal to the numerical value of the atomic mass from the periodic table 1 mole of C atoms= 12.0 g 1 mole of Mg atoms =24.3 g 1 mole of Cu atoms =63.5 g

12. Learning Check Give the molar mass to 1.0 mole A. 1 mole of Br atoms = ________ B.1 mole of Sn atoms = ________

13. Solution Give the molar mass to 0.1 g A. 1 mole of Br atoms =79.9 g/mole B.1 mole of Sn atoms =118.7 g/mole

14. Molar Mass of Compounds Both molecules and Ionic Compounds Mass in grams of 1 mole is equal to the sum of the atomic masses of all the atoms present 1 mole of CaCl 2 = 111.1 g/mole (1 mole Ca x 40.1 g/mole) + (2 moles Cl x 35.5 g/mole) 1 mole of N 2 O 4 = 92.0 g/mole (2 moles N x 14.0 g/mole) + (4 moles O x 16.0 g/mole)

15. Learning Check A. 1 mole of K 2 O = ______g B. 1 mole of antacid Al(OH) 3 = ______g

16. Solution A. 1 mole of K 2 O (2 K x 39.1 g/mole) + (1 O x 16.0 g/mole) = 94.2 g B. 1 mole of antacid Al(OH) 3 (1 Al x 27.0 g/mol) +(3 O x 16.0 g/mol) + (3 H x 1.0) = 78.0 g

17. Learning Check Prozac, C 17 H 18 F 3 NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. It has a molar mass of 1) 40.0 g/mole 2) 262 g/mole 3) 309 g/mole

18. Solution Prozac, C 17 H 18 F 3 NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. It has a molar mass of 17C (12.0) + 18H (1.0) + 3F (19.0) + 1N (14.0) + 1 O (16.0) 3) 309 g/mole

19. Determine the% composition of H 2 SO 4 1 – Calc the # grams in a mole of the formula 2 – Divide each of the elements total masses by the molar mass 3 – Mult by 100 to make a percent

20. Determine the percent composition of H 2 SO 4 H 2 x 1.0 g= 2.0 g 98.1 S 1 x 32.1 g= 32.1 g 98.1 O 4 x 16.0 g= 64.0 g 98.1 g/mol x 100 =

21. What is the percent composition of C 5 H 8 NO 4 MSG, a compound used to flavor foods and tenderize meats?

22. What is the percent composition of Ca(NO 3 ) 2

23. Molar Math Converting moles particle, and Converting moles mass

24. Convert 0.187 mol Na + to ions. 0.187 mol Na + 6.02 x 10 23 ions Na 1 ( ) = 1.13 x 10 23 ions Na

25. Convert 5.66 x 10 23 atoms Xe to moles. 5.66 x 10 23 atoms Xe ( ) = 0.940 mol Xe 6.02 x 10 23 atoms Xe 1 mole Xe

26. Moles = grams/molar mass Determine the number of moles in 27.35 g of the element sulfur. Calculate the number of moles of SiO 2 in a 18.95 g sample

27. Moles = grams/molar mass Determine the number of grams in 0.0595 moles of H 2 O ( mm = 18.0 g/mol)? Determine the number of grams in 1.83 x 10 -3 moles of SiO 2 (SiO 2 mm = 60.1 g/mol)

28. Learning Check The artificial sweetener aspartame (Nutri-Sweet) formula C 14 H 18 N 2 O 5 is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame?

29. Solution Molar mass of Aspartame C 14 H 18 N 2 O 5 (14 x 12.0) + (18 x 1.01) + (2 x 14.0) + (5 x 16.0) = 294 g/mole Setup moles = 225 g aspartame = 0.765 mol 294 g aspartame/mol = 0.765 mole aspartame

30. Moles and Grams Aluminum is often used for the structure of light-weight bicycle frames. How many grams of Al are in 3.00 moles of Al? 3.00 moles Al ? g Al

31. Setup grams = mol x molar mass 3.00 moles Al x 27.0 g Al = 81.0 g Al Mole Mass Conversions (grams = mol x molar mass)

32. Formulas

33. Chemical Formulas Include the symbols of the elements and the subscripts, which indicate the number of atoms, or ions, of each. Example: C 6 H 12 O 6 – Glucose Contains 6 atoms of Carbon, 12 atoms of Hydrogen and 6 atoms of Oxygen.

34. Any change to the symbols or suscripts changes the formula. Changing the formula changes the compound which is represented. Example: C 6 H 12 O 6 is Glucose! C 6 H 12 O 5 is Not Glucose! Chemical Formulas

35. Other Types of Formulas The formulas for compounds can also be expressed as: (1.) an empirical formula and as (2.) a molecular (true) formula. Empirical Molecular (true)Name CHC 2 H 2 acetylene CHC 6 H 6 benzene CO 2 CO 2 carbon dioxide CH 2 OC 5 H 10 O 5 ribose

36. Defining Empirical and Molecular Formula Empirical formula: A formula that shows the simplest whole-number ratio of atoms in the formula. Molecular formula: A formula that is a whole-number multiple of the empirical formula.

37. Learning Check A. What is the empirical formula for C 4 H 8 ? 1) C 2 H 4 2) CH 2 3) CH B. What is the empirical formula for C 8 H 14 ? 1) C 4 H 7 2) C 6 H 12 3) C 8 H 14 C. What is a molecular formula for CH 2 O? 1) CH 2 O2) C 2 H 4 O 2 3) C 3 H 6 O 3

38. Solution A. What is the empirical formula of C 4 H 8 ? 2) CH 2 B. What is the empirical formula of C 8 H 14 ? 1) C 4 H 7 C. What is a molecular formula of CH 2 O? 1) CH 2 O 2) C 2 H 4 O 2 3) C 3 H 6 O 3

39. 1. You need grams of each element to calculate the moles of each element. Assume you have a 100 g sample! 2. Calculate the number of moles of each element. 3. Find the smallest whole number ratio by dividing each mole value by the smallest mole values: 4. Write the simplest or empirical formula Determining Empirical Formulas

40. Finding the Empirical Formula A compound is 71.66% Cl, 24.28% C, and 4.06% H. The molar mass is known to be 99.0 g/mol. What is the empirical formula?

41. 1. Determine the number of grams of each element. 71.66 % Cl becomes 71.66 g Cl 24.28 % C becomes 24.28 g C 4.06 % H becomes 4.06 g H

42. 2. Calculate the number of moles of each element (divide by molar mass). 71.66 g Cl = 2.02 mol Cl 35.5 g/mol Cl 24.28 g C = 2.02 mol C 12.0 g/mol C 4.06 g H = 4.06 mol H 1.0 g/mol H

43. Why moles? Why do you need the number of moles of each element in the compound? The subscripts in the chemical formula will equal the mole to mole ratio of the elements present.

44. 3. Find the smallest whole number ratio by dividing each mole value by the smallest mole values: Cl: 2.02 = 1 Cl 2.02 C: 2.02 = 1 C 2.02 H: 4.06 = 2.005 H 2.02

45. 4. Write the simplest or empirical formula = CH 2 Cl

46. Determining a Molecular Formula from an Empirical Formula

47. In Order to Determine the Molecular Formula from the Empirical Formula you must have the mass of both the Molecular Formula and the Empirical Formula.

48. Empirical and Molecular Formulas Molar Mass of the molecular formula Molar Mass of the empirical formula or Empirical formula x n = Molecular formula = n

49. 5. Determine the molecular formula from the Empirical form of CH 2 Cl….remember,the formula mass was 99.0 g/mol. 1(C) + 2(H) + 1(Cl) = 1(12.0) + 2(1.0) + 1(35.5) = 49.5g/mol Determine multiplying factor = n mm molec form = 99.0 g/mol mm emp form 49.5 g/mol Solution: CH 2 Cl x 2 = C 2 H 4 Cl 2 n = = 2

50. Learning Check A compound has a formula mass of 176.0 and an empirical formula of C 3 H 4 O 3. What is the molecular formula?

51. Solution A compound has a formula mass of 176.0 and an empirical formula of C 3 H 4 O 3. What is the molecular formula? C 3 H 4 O 3 = 88.0 g/mol 176.0 g C 6 H 8 O 6 88.0 g = 2

52. Learning Check Aspirin is 60.0% C, 4.50 % H and 35.5% O. Calculate its Empirical formula.

53. Solution 60.0 g C = ______ mol C Molar mass C 4.50 g H = ______ mol H Molar mass H 35.5 g O = ______ mol O Molar mass O

54. Solution 60.0 g C = 5.00 mol C 12.0 g/mol C 4.50 g H = 4.50 mol H 1.01 g/mol H 35.5 g O = 2.22 mol O 16.0 g/mol O

55. 5.00 mol C= 2.25 2.22 mol O 4.50 mol H = 2.00 2.22 mol O 2.22 mol O = 1.00 2.22 mol O Are the results whole numbers?_____ Divide by the smallest # of moles.

56. Finding Subscripts A fraction between 0.1 and 0.9 must not be rounded if the given is in percents. Multiply all results by an integer to give whole numbers for subscripts. (1/2) 0.500 x 2 = 1 (1/3)0.333 x 3 = 1 (1/4)0.250 x 4 = 1 (3/4)0.750 x 4 = 3

57. Multiply everything x 4 C: 2.25 mol C x 4 = 9 mol C H: 2.00 mol Hx 4 = 8 mol H O: 1.00 mol O x 4 = 4 mol O Use the whole numbers of moles as the subscripts in the simplest formula C 9 H 8 O 4

58. Practice

59. Finding the Molecular Formula A compound is 71.65% Cl, 24.27% C, and 4.07% H. The molar mass is known to be 99.0 g/mol. What are the empirical and molecular formulas?

60. Calculate the empirical formula for the following compound 15.8% carbon and 84.2% sulfur

61. Calculate the empirical formula for the following compound 28.7% K, 1.5% H, 22.8% P and 47.0% O

62. Calculate the empirical formula for the following compound 43.6% phosphorus and 56.4% oxygen