2. 1 The Mole 6.02 X 10 23 Chemistry cp– Chapter 8

3. 2 STOICHIOMETRYSTOICHIOMETRY - the study of the quantitative aspects of chemical reactions.

4. 3 The Mole A counting unit Similar to a dozen, except instead of 12, it’s 602 billion trillion 602,000,000,000,000,000,000,000 6.02 X 10 23 (in scientific notation) Amedeo Avogadro (1776 – 1856)This number is named in honor of Amedeo Avogadro (1776 – 1856), who studied quantities of gases and discovered that no matter what the gas was, there were the same number of molecules present

5. 4 Just How Big is a Mole? Enough soft drink cans to cover the surface of the earth to a depth of over 200 miles. If you had Avogadro's number of unpopped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to a depth of over 9 miles. If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole.

6. 5 Everybody Has Avogadro’s Number! But Where Did it Come From? It was NOT just picked! It was MEASURED. One of the better methods of measuring this number was the Millikan Oil Drop Experiment Since then we have found even better ways of measuring using x- ray technology

7. 6 Suppose we invented a new collection unit called a rapp. One rapp contains 8 objects. 1. How many paper clips in 1 rapp? a) 1b) 4c) 8 2. How many oranges in 2.0 rapp? a) 4b) 8c) 16 3. How many rapps contain 40 gummy bears? a) 5b) 10c) 20 Learning Check

8. 7 1. How many pencils are in 1 dozen pencils? a) 1b) 12c) 6.02 x 10 23 2. How many pencils are in 1 mole pencils? a) 1b) 12c) 6.02 x 10 23 3. How many carbon atoms are in 1 molecule of C 2 H 6 ? a) 1b) 2c) 6.02 x 10 23 4. How many carbon atoms are in 1 mole of C 2 H 6 ? a) 1b) 2c) 1.204 x 10 24 Learning Check

9. 8 The Mole 1 dozen cookies = 12 cookies 1 mole of cookies = 6.02 X 10 23 cookies 1 dozen cars = 12 cars 1 mole of cars = 6.02 X 10 23 cars 1 dozen Al atoms = 12 Al atoms 1 mole of Al atoms = 6.02 X 10 23 atoms Note that the NUMBER is always the same, but the MASS is very different! Mole is abbreviated mol (gee, that’s a lot quicker to write, huh?)

10. 9 = 6.02 x 10 23 C atoms = 6.02 x 10 23 H 2 O molecules = 6.02 x 10 23 NaCl formula units (technically, ionics are compounds and are called formula units, but some worksheets use “molecules”) 6.02 x 10 23 Na + ions and 6.02 x 10 23 Cl – ions A Mole of Particles A Mole of Particles Contains 6.02 x 10 23 particles 1 mole C 1 mole H 2 O 1 mole NaCl

11. 10 6.02 x 10 23 particles 1 mole or 1 mole 6.02 x 10 23 particles Note that a particle could be an atom OR a molecule! Avogadro’s Number as Conversion Factor

12. 11 1. Number of atoms in 0.500 mole of Al a) 500 Al atoms b) 6.02 x 10 23 Al atoms c) 3.01 x 10 23 Al atoms 2.Number of moles of S in 1.8 x 10 24 S atoms a) 1.0 mole S atoms b) 3.0 mole S atoms c) 1.1 x 10 48 mole S atoms Learning Check

13. 12 1. Number of atoms in 0.500 mole of Al 0.500 mol Al x 6.02 x 10 23 Al atoms = 1 mole Al atoms 2.Number of moles of S in 1.8 x 10 24 S atoms 1.8 x 10 24 S atoms x 1 mole S atoms = 6.02 x 10 23 S atoms Learning Check

14. 13 1.How many Al atoms are in 15.8 mole of Al? 15.8 mole Al x 6.02 x 10 23 Al atoms = 1 mole Al 2.How many moles are in 3.69 x 10 16 S atoms? 3.69 x 10 16 S atoms x 1 mole S = 6.02 x 10 23 S atoms Learning Check

15. 14 The Mass of 1 mole (in grams) Equal to the numerical value of the average atomic mass (get from 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 Where are these numbers from? PERIODIC TABLE Molar Mass

16. 15 Other Names Related to Molar Mass Molecular Mass/Molecular Weight: Single molecule, mass is measured in amu’s instead of grams. But, the molecular mass/weight is the same numerical value as 1 mole of molecules. Only the units are different Formula Mass/Formula Weight: Same goes for compounds. But again, the numerical value is the same. Only the units are different.

17. 16 Other Names Related to Molar Mass THE POINT: You may hear all of these terms which mean the SAME NUMBER… just different units Molar Mass = Gram Formula Weight in our textbook With Avogadro’s #, you may also hear the terms: molecules, atoms, formula units, ions, particles, “things” IT DEPENDS ON WHAT YOU’RE TALKING ABOUT: example: 1 dozen eggs versus 1 dozen roses 1 mole of H 2 O molecules vs. 1 mole of NaCl formula units

18. 17 Find the molar mass (usually we round to the tenths place) Learning Check! A.1 mole of Br atoms B.1 mole of Sn atoms =79.9 g/mole = 118.7 g/mole

19. 18 Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole of CaCl 2 = 111.1 g/mol (1 mole Ca x 40.1 g/mol ) + (2 moles Cl x 35.5 g/mol) = 111.1 g/mol CaCl 2 Molar Mass of Molecules and Compounds

20. 19 Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole of N 2 O 4 Molar Mass of Molecules and Compounds = 92.0 g/mol

21. 20 A.Molar Mass of K 2 O = ? grams/mole B. Molar Mass of antacid Al(OH) 3 = ? grams/mole K 2 O = 94.2 g/molAl(OH) 3 = 78.0 g/mol Learning Check!

22. 21 Prozac, C 17 H 18 F 3 NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. Find its molar mass. 309.0 grams Learning Check

23. 22 molar mass Grams Moles Calculations with Molar Mass Do you multiply or divide by molar mass? It depends on which way you’re going. Use conversion factors.

24. 23 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 Converting Moles and Grams

25. 24 1.Molar mass of 1 mole Al = 27.0 g Al 2. Conversion factors for Al 27.0 g Al or 1 mol Al 1 mol Al 27.0g Al 3. Setup3.00 moles Al x 27.0 g Al = 1 mole Al Answer = 81.0 g Al

26. 25 Iron (III) oxide is often called rust, it forms when iron metal reacts with moisture. How many moles of Fe 2 O 3 are in 3.00 grams of Fe 2 O 3 ? 3.00 grams of Fe 2 O 3 ? moles Fe 2 O 3 Converting Moles and Grams

27. 26 1. Molar mass of Fe 2 O 3 YOU MUST CALCULATE IT! 2. Conversion factors for Fe 2 O 3 ? g Fe 2 O 3 or 1 mol Fe 2 O 3 1 mol Fe 2 O 3 ? g Fe 2 O 3 3. Setup3.00 grams Fe 2 O 3 x 1 moleFe 2 O 3 ? grams Fe 2 O 3 Answer = 0.0188 mol Fe 2 O 3

28. 27 1. Molar mass of Fe 2 O 3 159.6 grams 2. Conversion factors for Fe 2 O 3 159.6 g Fe 2 O 3 or 1 mol Fe 2 O 3 1 mol Fe 2 O 3 159.6 g Fe 2 O 3 3. Setup3.00 grams Fe 2 O 3 x 1 moleFe 2 O 3 159.6 g Fe 2 O 3 Answer = 0.0 188 mole Fe 2 O 3

29. 28 The artificial sweetener aspartame (Nutra-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? Learning Check!

30. 29 225 g C 14 H 18 N 2 O 5 = ? mol C 14 H 18 N 2 O 5 225g x _?__mol__ = mol ? g Setting it up: Do you know a relationship between moles and grams for C 14 H 18 N 2 O 5 ?

31. 30 225 g C 14 H 18 N 2 O 5 = ? mol C 14 H 18 N 2 O 5 The relationship is: MOLAR MASS! 1 mol = the sum of the atomic masses from the periodic table in grams! 225g x _1__mol__ = ? mol ? g Setting it up:

32. 31 225 g C 14 H 18 N 2 O 5 = ? mol C 14 H 18 N 2 O 5 225g x _1__mol__ = ? mol 294.3 g How do you enter this in your calculator? Setting it up: Enter first number first, multiply numerators, divide by denominators. 225 x 1 / 294.3 =

33. 32 Atoms/Molecules and Grams Since 6.02 X 10 23 particles = 1 mole AND 1 mole = molar mass (grams) You can convert atoms/molecules to moles and then moles to grams! (Two step process) You can’t go directly from atoms to grams!!!! You MUST go thru MOLES.

34. 33 molar mass Avogadro’s number Grams Moles particles Everything must go through Moles!!! Calculations

35. 34 Atoms/Molecules and Grams How many atoms of Cu are present in 35.4 g of Cu? 35.4 g Cu 1 mol Cu 6.02 X 10 23 atoms Cu 63.5 g Cu 1 mol Cu = 3.4 X 10 23 atoms Cu

36. 35 Learning Check! How many atoms of O are present in 78.1 g of oxygen (O 2 )? 78.1 g O 2 1 mol O 2 6.02 X 10 23 molecules O 2 2 atoms O 32.0 g O 2 1 mol O 2 1 molecule O 2

37. 36 Learning Check! How many atoms of K are present in 78.4 g of K?

38. 37 Learning Check! What is the mass (in grams) of 1.20 X 10 24 molecules of glucose (C 6 H 12 O 6 )?

39. 38 Molar Volume New fact: For gases at STP: 0 o C and 1 atm. (a standard temperature and pressure) 1 mole = 22.4 L (our textbook uses dm 3 ) This creates two NEW conversion factors! 22.4 L OR 1 mole 1 mole 22.4 L

40. 39 Molar Volume How many liters are in 5 moles of nitrogen dioxide gas at STP? Start with given number and unit. Chose a conversion factor. 22.4 L OR 1 mole 1 mole 22.4 L Cancel the units. Do the math. 5 mol NO 2 x 22.4 L NO 2 = 1 mol NO 2

41. 40 Molar Volume How many moles are in 0.67 liters of carbon monoxide gas at STP? Start with given number and unit. Chose a conversion factor. 22.4 L OR 1 mole 1 mole 22.4 L Cancel the units. Do the math. 0.67 L CO x 1 mol CO = 22.4 L

42. 41 Molar Volume & Molar Mass How many grams are in 0.67 liters of carbon monoxide gas at STP? Now, you need to stack up two conversion factors together. First is molar volume, then is molar mass, (which you have to calculate!) 0.67 L CO x 1 mol CO x ? grams CO = 22.4 L 1 mol CO = 0.84 g carbon monoxide

43. 42 Molarity, M New fact: For liquid solutions (typically “aqueous”, the substance dissolved in water) 1 L = # mol The # is given as “M” or molarity For examples: A 5.0 M solution means : 5.0 moles = 1 L 1 L OR 5.0 mol 5.0 mol 1 L A 0.37 M solution means : 5.0 moles = 1 L 1 L OR 0.37 mol 0.37 mol 1 L

44. 43 Molarity, M For liquid solutions 1 L = # mol The # is given as “M” or molarity This CHANGES based on the problem given. How many moles are in 7.0 L of a 4.0 M solution of NaCl? 7.0 L NaCl solution 4.0 mol NaCl solution 1 L NaCl solution x

45. 44 Molarity, M For liquid solutions 1 L = # mol The # is given as “M” or molarity This CHANGES based on the problem given. How many moles are in 7.0 L of a 1.5 M solution of NaCl? 7.0 L NaCl solution 1.5 mol NaCl solution 1 L NaCl solution x

46. 45Homework

47. 46 What is the percent carbon in C 5 H 8 NO 4 (the glutamic acid used to make MSG monosodium glutamate), a compound used to flavor foods and tenderize meats? a) 8.22 %C b) 24.3 %C c) 41.1 %C Percent Composition

48. 47 Chemical Formulas of Compounds (HONORS only) Formulas give the relative numbers of atoms or moles of each element in a formula unit - always a whole number ratio (the law of definite proportions).Formulas give the relative numbers of atoms or moles of each element in a formula unit - always a whole number ratio (the law of definite proportions). NO 2 2 atoms of O for every 1 atom of N NO 2 2 atoms of O for every 1 atom of N 1 mole of NO 2 : 2 moles of O atoms to every 1 mole of N atoms If we know or can determine the relative number of moles of each element in a compound, we can determine a formula for the compound.If we know or can determine the relative number of moles of each element in a compound, we can determine a formula for the compound.

49. 48 Types of Formulas (HONORS only) Empirical FormulaEmpirical Formula The formula of a compound that expresses the smallest whole number ratio of the atoms present. Ionic formula are always empirical formula Molecular FormulaMolecular Formula The formula that states the actual number of each kind of atom found in one molecule of the compound.

50. 49 To obtain an Empirical Formula (HONORS only) 1.Determine the mass in grams of each element present, if necessary. 2.Calculate the number of moles of each element. 3.Divide each by the smallest number of moles to obtain the simplest whole number ratio. 4.If whole numbers are not obtained * in step 3), multiply through by the smallest number that will give all whole numbers * Be careful! Do not round off numbers prematurely

51. 50 A sample of a brown gas, a major air pollutant, is found to contain 2.34 g N and 5.34g O. Determine a formula for this substance. require mole ratios so convert grams to moles moles of N = 2.34g of N = 0.167 moles of N 14.0 g/mole 14.0 g/mole moles of O = 5.34 g = 0.334 moles of O 16.0 g/mole 16.0 g/mole Formula: Formula: (HONORS only)

52. 51 Calculation of the Molecular Formula (HONORS only) A compound has an empirical formula of NO 2. The colourless liquid, used in rocket engines has a molar mass of 92.0 g/mole. What is the molecular formula of this substance?

53. 52 Empirical Formula from % Composition (HONORS only) A substance has the following composition by mass: 60.80 % Na ; 28.60 % B ; 10.60 % H What is the empirical formula of the substance? Consider a sample size of 100 grams This will contain 28.60 grams of B and 10.60 grams H Determine the number of moles of each Determine the simplest whole number ratio