Introduction to the mole and molar mass Get you calculator Introduction to the mole and molar mass Get you calculator. You’re going to need it! Mr.H Revised 15-11-2015

L.O: Have a conceptual understanding of the mole as the method of “counting” items and finding the mass of item. Be able to calculate the number of moles if given the number of items. Be able to calculate the mass of a sample if given the number of moles in a sample. Be able to determine the molar mass of a compound.

Background When you buy eggs you usually ask for a _______ eggs. You know that one dozen of any item is ______. Dozen 12 http://www.eggs.ab.ca/news/images/mediathumbs/basic6.jpg

Paper Paper is packaged by a ream. A ream of paper has 500 sheets. Why is it useful to use units like a dozen or a ream? Image source: http://images.amazon.com/images/P/B0007GGUYW.01-A1HIK9Y0Y9Y0JC._SCLZZZZZZZ_.jpg

What determines how many items should make up a particular unit?

If you were asked to design a new unit to count something, what would you consider when choosing how many items should be included in your new counting unit?

Materials 3 packages of different types of candy, balance, worksheet, calculator, pencil.

Part 1 Record the number of items in each package. Measure the mass of each package. Record the mass of each package in the data table. Answer questions in Analysis and Interpretations. Record masses your group measured on the board summarizing class data.

Number of items in package Data Table 1 Name of the Items in the Package Number of items in package Mass of the package Jolly Ranchers Caramels Hershey's Kisses 26.9 4 23.03 4 20.96 4

ANALYSIS AND INTERPRETATION As you know, a dozen represents 12 items. Since I did not have enough items to make a dozen, I decided to make a new counting unit. I called this unit a MANU. Each of your packages contains _____ items. 4

1. A MANU of oranges will have _____ oranges. 4 Image Source: http://www.geomembrane.com/040205%20Picking%20Oranges%20047.jpg

2. A MANU of pretzels has ____ pretzels. 4 Image Source: http://www.gannon.edu/resource/meetwus/images/pretzels.jpg

3. A MANU of molecules of water has ____ molecules of water. 4 Image Source: http://www.nyu.edu/pages/mathmol/library/water/water.gif

4. A MANU of particles has ___ particles. http://birdsofsanibel.free.fr/Images/2001-2002/Burrowing%20MANU%201%202001-2002.jpg 4. A MANU of particles has ___ particles. 4

5. A MANU of atoms of iron has _____ atoms of iron. 4 26 Fe 55.85 Image Source: http://www.geo.msu.edu/geo333/images/iron-ore-closeup.jpg

6. A MANU of formula units of salt has _______ formula units of salt. 4 Image Source: http://www.emporia.edu/earthsci/museum/salt.jpg

7. How many Hershey’s Kisses are in 2 MANUS? _______ 8 Image Source: SStevens 2005

8. How many caramels are in 10 MANUS? _______ 40 Image source: SStevens 2005

9. How many Dum Dum Pops are in 400 MANUS? _______ 1600 Image Source: http://www.conway.com/ssinsider/images/pw030616c.jpg

10. How many Starbursts are in 1/2 MANU? _____ Image source: SStevens 2005

11. Write the formula for finding the number of items (x), if given the number of MANUS (n) X = 4n

12. How many oranges are in 5 MANUS? _______ 20 Image Source: http://www.geomembrane.com/040205%20Picking%20Oranges%20047.jpg

13. How many apples are in 0.5 MANUS? _______ 2 Image Source: http://www.vivitar.com/Products/DigCams/Galleries/V3632/V3632Gal/apples.jpg

14. How many pencils are in 0.25 (1/4) MANUS? ___ Image Source: http://tmc.southern.edu/pictures/pencils.jpg

15. How many atoms of silver are in 20 MANUS? _______ 80 47 Ag 107.9 Image Source: http://mineral.galleries.com/minerals/elements/silver/silver.jpg

16. How many molecules of water are in 5 MANUS? _______ 20 Image Source: http://www.nyu.edu/pages/mathmol/library/water/water.gif

17. How many MANUS are 16 Hershey’s Kisses? ______ 4 Image Source: SStevens 2005

18. How many MANUS are 100 pretzels? ____ 25 Image Source: http://www.gannon.edu/resource/meetwus/images/pretzels.jpg

19. How many MANUS are 400 lulu icecreams? ____ 100 Image Source: SStevens 2005

20. How many MANUS is 1 orange? ________ (Write a fraction or a decimal.) ¼ 0.25 Image Source: http://www.geomembrane.com/040205%20Picking%20Oranges%20047.jpg

21. How many MANUS are 2 caramels? _____ 0.5 Image Source: SStevens 2005

22. Write your own formula for finding the number of MANUS (x) given the number of pieces (n) X = n/4

23. How many MANUS are 48 Hershey’s Kisses? ____ 12 Image Source: SStevens 2005

24. How many MANUS are 32 Hershey’s Kisses? ______ 8 Image Source: SStevens 2005

25. How many MANUS are 24 Jolly Ranchers? ______ 6 Image Source: SStevens 2005

26. How many MANUS are 2 Gobstoppers? ______ .5 Image Source: SStevens 2005

27. How many MANUS are 20 caramels? ______ 5 Image Source:Sstevens 2005

MANUS MANU of molecules of water would be too small to see. Scientists had to select a bigger unit for counting molecules of substances. The unit scientists use is called a MOLE.

One MOLE of anything has 602,200,000,000,000,000,000,000 items. Image Sources: http://www.moleday.org/htdocs/gifs/moldy.gif

6.022 x 1023 One MOLE of anything has 6.022 x 1023 items. AVOGADRO’S NUMBER 6.022 x 1023 One MOLE of anything has 6.022 x 1023 items.

28. How many Hershey’s Kisses make up 1 MOLE? 6.022 x 1023 Image Source: SStevens 2005

29. How many caramels make up 10 MOLES? 10 x [6.022 x 1023] 60.22 x 1023 Or 6.022 x 1024 Both correct!

30. Find the number of Jolly Ranchers in 4 MOLES. 4 [6.022 x 1023] 24.088 x 1023 2.41 x 1024

31. Find the number of atoms of sodium in 2 MOLES. 2[6.022 x 1023 ] 12.044 x 1023 1.20 x 1024 11 Na 22.99

32. Find the number of molecules of water in 6 MOLES. 6[6.022 x 1023] 36.113 x 1023 3.61 x 1024

33. Find the number of caramels in 0.5 MOLES. .5 x [6.022 x 1023 ] 3.011 x 1023 Image Source: SStevens

34. How many moles of caramels is 6.022x1023 of caramels? ___ Image Source: SStevens 2005

35. How many moles of Starbursts is 6.022x1023 of Starbursts? ___

Avagadro is a bad boy!

36. How many moles of Gobstoppers is 12.04x1023 of Gobstoppers? ___

37. How many atoms of potassium make up one MOLE? 6.022 x 1023 19 K 39.10

38. How many atoms of potassium make up 2 MOLES? 2 x [6.022 x 1023 ] 12.044 x 1023 1.20 x 1024 19 K 39.10

39. How many molecules of water make up 1 MOLE? 6.022 x 1023 Image Source: http://www.nyu.edu/pages/mathmol/library/water/water.gif

40. How many molecules of water make up 5 MOLES? 5 x [6.022 x 1023 ] 30.110 x 1023 3.01 x 1024

41. How many moles are 6.022 x 1023 atoms of sodium? _____ Image source: SStevens 2002

42. How many moles are 12.04 x 1023 atoms of carbon? _____ Image source: SStevens 2002

43. How many moles are 18.06 x 1023 atoms of sodium? _____ Image source: SStevens 2002

44. How many moles are 60.22 x 1023 atoms of sodium? _____ Image source: SStevens 2002

45. How many moles are 6.022 x 1023 molecules of water? _____ Image Source: http://www.nyu.edu/pages/mathmol/library/water/water.gif

46. How many moles are 12.04 x 1023 molecules of water? _____ Image Source: http://www.nyu.edu/pages/mathmol/library/water/water.gif

47. How many moles are 30.10 x 1023 molecules of water? _____ 5 30.10 x 1023 = 5 6.022 x 1023 Image Source: http://www.nyu.edu/pages/mathmol/library/water/water.gif

Part 2

Mass In addition to being able to tell the number of items in an MANU, you can now tell the mass of an MANU of Hershey’s Kisses, Jolly Ranchers, and caramels.

Number of items in package Data Table 1 Name of the Items in the Package Number of items in package Mass of package Jolly Ranchers Caramels Hershey's Kisses 4 26.9 4 23.03 4 20.96

48. Based on your measurements, the mass of 1 MANU of Hershey’s Kisses is ______ g. 20.96 Image Source: SStevens 2005

49. The mass of 2 MANUS of Hershey’s Kisses is ______ g. 41.92 Image Source: SStevens 2005

50. The mass of 1 MANU of Jolly Ranchers is ___ g. 26.9 Image Source: SStevens 2005

51. The mass of 1 MANU of caramels is ____ g 23.03 Image source: http://images.amazon.com/images/P/B0004LYM3G.01-A3CDPEGSIQM61V._SCMZZZZZZZ_.jpg

52. The mass of 100 MANUS of Hershey’s Kisses is ____ g. 2096 Image Source: SStevens 2005

53. The mass of 1/2 MANU of Hershey’s Kisses is _________ g. 10.48 Image Source: SStevens

54.a. Complete the directions for finding total mass (MT) of a given number of MANUS (n), assuming you know the mass of a single MANU (m) MT = m x n

54.b. Complete the formula for finding total mass (MT) of a given number of items (z), assuming you know the mass of a single MANU (m) MT = m x (z/4)

55. The mass of 4 MANUS of Jolly Ranchers is _______ g. 107.6 Image Source: SStevens2005

56. The mass of 0.5 MANUS of Jolly Ranchers is ______ g. 13.45 Image Source: SStevens 2005

57. The mass of 100 MANUS of caramels is ________ g. 2303.00 Image source: SStevens 2005

58. The mass of 1/5 MANUS of caramels is ________ g. 4.606 Image source: SStevens 2005

59. The mass of 60 MANUS of Hershey’s Kisses is ________ g. 1257.6 Image Source: SStevens

60. The mass of 0.1 MANUS of Hershey’s Kisses is ________ g. 2.096 Image Source: SStevens 2005

61. How would you calculate the number of MANUS if you know the mass of a package of Hershey’s Kisses? Image Source: http://www.conway.com/ssinsider/images/pw030616c.jpg Divide total by mass of single MANU e.g 260/20.96 = 12.40

62. How would you calculate the number of MANUS if you know the mass of a package of caramels? Image Source: SStevens 2005 198.5/23.03 = 8.62

63. How would you calculate the number of MANUS if you know the mass of a package of Jolly Ranchers? 198/26.9 = 7.36

Molar Mass Scientists use the Periodic Table to determine the mass of a mole of atom of an element. For example, a mole of Iron (Fe) atoms would have a mass of 55.85g.

Amazing!

Periodic Table Image Source:http://www.webelements.com/

64. The mass of 1 mole of Strontium (Sr) is ___ g. 87.62 38 Sr 87.62

65. The mass of 1 mole of Lead (Pb) is ____ g. 207.2 82 Pb 207.2

66. The mass of 1 mole of Nickel (Ni) is ____ g. 58.69 28 Ni 58.69

67. The mass of 4 moles of Strontium (Sr) is ______g. 350.48 38 Sr 87.62

68. The mass of 0.5 moles of Lead (Pb) is ____ g. 103.6 82 Pb 207.2

69. The mass of 100 moles of (Ni) is ________ g. 5869.00 28 Ni 58.69

Molar Mass Scientists also use the Periodic Table to determine the molar mass (formula weight) of compounds. The molar mass of the compound is the sum of the molar masses of the elements that make up the compound.

Potassium Chloride The molar mass of Potassium Chloride (KCl) is : Potassium (K) 39.10 g/mole Chloride (Cl) + 35.45 g/mole 74.55 g/mole

Potassium Permanganate The molar mass of KMnO4 is the sum of all the molar masses times the number of atoms of each element for the molecule (subscript).

Potassium Permanganate KMnO4 Potassium (K) 39.10 g/mole Manganese (Mn) 54.94g/mole Oxygen (O) 4 x [16.00 g/mole] TOTAL 158.04 g/mole.

70. The molar mass of 1 mole of Sodium Chloride (NaCl) is____ g. 58.44 Image source: SStevens 2002

71. The molar mass of 1 mole of Lead Iodide (PbI2) is _____ g. 461.0

72. The mass of 100 moles of Nickel Sulfide (NiS) is ________ g. 9076.00

73. The mass of 1 mole of is Glucose (C6H12O6) is ________ g. 180.156 Image source: SStevens 2002

Plants make approximately 24 kgs of glucose per person per year!

74. The mass of 1 mole of is Sucrose (C12H24O12 ) _______ g. 306.31 Image source: http://www.southernmatters.com/sugarcane/images/sucrose2.jpg

75. The mass of 4 moles of Glucose (C6H12 O6) is _________ g. 720.624 Image source: SStevens 2002

Mole Conversions In chemistry, the mole is the standard measurement of amount. However, balances DO NOT give readings in moles. Balances give readings in grams. So the problem is that, while we compare amounts of one substance to another using moles, we must also use grams, since this is the information we get from balances.

There are three steps to converting grams of a substance to moles. 1. Determine how many grams are given in the problem. 2. Calculate the molar mass of the substance. 3. Divide step one by step two.

The three steps above can be expressed in the following proportion: Grams Moles --------------- = -------------- Molar Mass 1 Mole

Example #1 - Convert 25 grams of KMnO4 to moles. Step One: The problem will tell you how many grams are present. Look . for the unit of grams. The problem gives us 25.0 grams. Step Two: You need to know the molar mass of the substance. The . , molar mass of KMnO4 is 158.034 grams/mole. Potassium (K) = 39.10 x 1 = 39.10 g Manganese (Mn) = 54.94 x 1 = 54.94 g Oxygen (O) = 16.00 x 4 = 64.00 g --------------- 158.04 g Step Three: You divide the grams given by the substance's molar mass . . (25.0/158.04) The answer of 0.16 mole has been rounded off.

Example #2 - Calculate how many moles are in 57.0 grams of Mg(NO3)2 1) 57.0 grams are given in the text of the problem. 2) The molar mass is 148 grams/mole. Mg (Magnesium) : 24 x 1=24 g N (Nitrogen) : 14 x 2=28 g O (Oxygen) : 16 x 6=96 g 3) Again you divide the grams by the substances molar mass (57.0 g/148 g). This answer has been rounded to 0.39 moles.

Practice Problems

1. Calculate the moles present in: 2.00 grams of H2O .11 moles water

2. Calculate the moles present in: 75.57 grams of KBr .635 moles KBr

3. Calculate the moles present in: 100.0 grams of KClO4 .72 moles KClO4

4. Calculate the moles present in: 225.5 grams of Sucrose (C12H24O12) .63 moles Sucrose

5. Calculate the moles present in: 350.0 grams of Glucose (C6H12O6) 1.943 moles Glucose

Calculate the mass of oxygen needed to react with 12 grams of magnesium. Step 1: Write Ar values: Mg = 24; O = 16 Step 2: Write the formula and balance it Mg + O2  MgO (not balanced) 2Mg + O2  2MgO (balanced ) Step 3: Write the formula and balance it 48g of magnesium reacts with 32g of oxygen Therefore, (12/48)x32 = 8g of oxygen needed! √

Calculate the amount of aluminium needed to react with 34g of oxygen in aluminium oxide. (remember to work out the formula first!) 38.25 g

Homework

1. Calculate the moles present in: 3.00 grams of NaCl

2. Calculate the moles present in: 25.0 grams of NH3 1.47 moles NH3

3. Calculate the moles present in: 16.0 grams of KCl .21 moles KCl

4. Calculate the moles present in: 30.25 grams of BeCl2 .38 moles KCl

5. Calculate the moles present in: 175.25 grams of Li2S 3.81 moles Li2S

6. Calculate the moles present in: 75.62 grams of CO2 1.72 moles CO2

7. Calculate the moles present in: 56.5 grams of H2O 3.14 moles H2O

8. Calculate the moles present in: 22.6 grams of CH3COOH .38 moles CH3COOH

9. Calculate the moles present in: 18.4 grams of AgCl .13 moles AgCl

10. Calculate the moles present in: 68.3 grams of HCN 2.53 moles HCN