2. 1 The Mole 6.02 X 10 23 Unit 10 Chapter 11 SAVE PAPER AND INK!!! When you print out the notes on PowerPoint, print "Handouts" instead of "Slides" in the print setup. Also, turn off the backgrounds (Tools>Options>Print>UNcheck "Background Printing")!

3. 2 DIMENSIONAL ANALYSIS MHS Chemistry Chapter 4

4. 3 Conversion Factors Fractions in which the numerator and denominator are EQUAL quantities expressed in different units Example: 1 in. = 2.54 cm Factors: 1 in. and 2.54 cm 2.54 cm 1 in.

5. 4

6. 5 How many minutes are in 2.5 hours ? Conversion factor 2.5 hr x 60 min = 150 min 1 hr 1 hr cancel By using dimensional analysis / factor-label method, the UNITS ensure that you have the conversion right side up, and the UNITS are calculated as well as the numbers!

7. 6 Sample Problem You have $7.25 in your pocket in quarters. How many quarters do you have?You have $7.25 in your pocket in quarters. How many quarters do you have? 7.25 dollars 4 quarters 7.25 dollars 4 quarters 1 dollar 1 dollar X = 29 quarters

8. 7 Learning Check Write conversion factors that relate each of the following pairs of units: 1. Liters and mL 2. Hours and minutes 3. Meters and kilometers

9. 8 Learning Check A rattlesnake is 2.44 m long. How long is the snake in cm? a) 2440 cm b)244 cm c)24.4 cm

10. 9 Learning Check How many seconds are in 1.4 days? Unit plan: days hr min seconds 1.4 days x 24 hr x ?? 1 day

11. 10 Wait a minute! What is wrong with the following setup? 1.4 day x 1 day x 60 min x 60 sec 24 hr 1 hr 1 min 24 hr 1 hr 1 min

12. 11 English and Metric Conversions If you know ONE conversion for each type of measurement, you can convert anything!If you know ONE conversion for each type of measurement, you can convert anything! You must use these conversions:You must use these conversions: –Mass: 454 grams = 1 pound –Length: 2.54 cm = 1 inch –Volume: 0.946 L = 1 quart

13. 12 Learning Check An adult human has 4.65 L of blood. How many gallons of blood is that? Unit plan: L qt gallon Equalities:1 quart = 0.946 L 1 gallon = 4 quarts Your Setup:

14. 13 Solution Unit plan: L qt gallon Setup: 4.65 L x 1 qt x 1 gal = 1.23 gal 0.946 L 4 qt 0.946 L 4 qt

15. 14 Steps to Problem Solving Read problem Read problem Identify data Identify data Make a unit plan from the initial unit to the desired unit Make a unit plan from the initial unit to the desired unit Select conversion factors Select conversion factors Change initial unit to desired unit Change initial unit to desired unit Cancel units and check Cancel units and check Do math on calculator Do math on calculator Give an answer using significant figures Give an answer using significant figures

16. 15 Dealing with Two Units – Pre- AP Only If your pace on a treadmill is 65 meters per minute, how many seconds will it take for you to walk a distance of 8450 feet? 8450 ft 1m 1 min60 sec 13.28 ft65m1 min

17. 16 STOICHIOMETRYSTOICHIOMETRY - the study of the quantitative aspects of chemical reactions.

18. 17 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

19. 18 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.

20. 19 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

21. 20 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?)

22. 21 Suppose we invented a new collection unit called an ermis. One ermis contains 8 objects. 1. How many paper clips in 1 ermis? a) 1b) 4c) 8 2. How many oranges in 2.0 ermis? a) 4b) 8c) 16 3. How many ermis’ contain 40 gummy bears? a) 5b) 10c) 20 Learning Check

23. 22 = 6.02 x 10 23 C atoms = 6.02 x 10 23 H 2 O molecules = 6.02 x 10 23 NaCl “molecules” (technically, ionics are compounds not molecules so they are called formula units) 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

24. 23 Moles of elements 1 mol Mg = 6.02 x 10 23 Mg atoms 1 mol Au = 6.02 x 10 23 Au atoms Moles of compounds 1 mol NH 3 = 6.02 x 10 23 NH 3 molecules 1 mol C 9 H 8 O 4 = 6.02 x 10 23 aspirin molecules Examples of Moles

25. 24 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

26. 25 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

27. 26 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 Some people used to call this a “GFM” (gram formula mass) when used with ionic compounds Molar Mass

28. 27 Other Names Related to Molar Mass Molecular Mass/Molecular Weight: If you have a 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. (This is the beauty of Avogadro’s Number!) Formula Mass/Formula Weight: Same goes for compounds. But again, the numerical value is the same. Only the units are different. THE POINT: You may hear all of these terms which mean the SAME NUMBER… just different units

29. 28 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

30. 29 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 of N 2 O 4 = 92.0 g/mol Molar Mass of Molecules and Compounds

31. 30 A.Molar Mass of K 2 O = ? Grams/mole B. Molar Mass of antacid Al(OH) 3 = ? Learning Check!

32. 31 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. Learning Check

33. 32 molar mass Grams Moles Calculations with Molar Mass

34. 33 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

35. 34 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!

36. 35 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. That’s like asking 2 dozen cookies weigh how many ounces if 1 cookie weighs 4 oz? You have to convert to dozen first!

37. 36 molar mass Avogadro’s number Grams Moles particles Everything must go through Moles!!! Calculations

38. 37 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

39. 38 Learning Check! How many atoms of K are present in 78.4 g of K? 78.4 g K 1 mol K 6.02 X 10 23 atoms K 39.1 g K 1 mol K = 1.20 X 10 24 atoms K

40. 39 Learning Check! How many atoms of O are present in 78.1 g of oxygen?

41. 40 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

42. 41 Molar mass C 5 H 8 NO 4 = 146.0 g/mole % = total g C x 100 total g C 5 H 8 NO 4 = 60.0 g C x 100 = 41.1% C 146.0 g C 5 H 8 NO 4 Solution

43. 42 Chemical Formulas of Compounds 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 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.

44. 43 Types of Formulas 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.

45. 44 To obtain an Empirical Formula 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

46. 45 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 14.01 g/mole 14.01 g/mole moles of O = 5.34 g = 0.334 moles of O 16.00 g/mole 16.00 g/mole Formula: Formula:

47. 46 Calculation of the Molecular Formula 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? empirical formula mass: 14.01+2 (16.00) = 46.01 g/mol n = molar mass = 92.0 g/mol emp. f. mass 46.01 g/mol n = 2 2(NO 2 ) = N 2 O 4

48. 47 Empirical Formula from % Composition 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