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The Mole

The Mole. 6.02 X 10 23. 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)

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The Mole

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  1. The Mole 6.02 X 1023

  2. 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 1023 (in scientific notation) • This number is named in honor of Amedeo _________ (1776 – 1856), who studied quantities of gases and discovered that no matter what the gas was, there were the same number of molecules present

  3. Just as a dozen eggs equals 12 eggs, a mole = 602,000,000,000,000,000,000,000 • It is equal to that number no matter what kind of particles you’re talking about • It could be represent marbles, pencils, or bikes • usually deals with atoms and molecules • The word “mole” was introduced about 1896 by Wilhelm Oswald, who derived the term from the latin word moles meaning a “heap” or “pile.” • The mole, whose abbreviation is “mol”, is the SI base unit for measuringamount of a pure substance.

  4. The mole, as a unit, is only used to count very small items • Represents a # of items, so, we can know exactly how many items are in 1 mole • The experimentally determined number a mole is called, Avogadro’s Number. • Or6.02x1023 • The term representative particle refers to the species present in a substance • Usually atoms • Molecules • Or formula units(ions)

  5. How Do We Use The Mole? • We’d never use the mole to describe macroscopic or real world objects. • 1 mole (6.02x1023) of watermelon seeds would be found inside a watermelon the size of the moon. • 1 mole (6.02x1023) of donut holes would cover the earth and would be 5 miles deep. • Since the mole is such a huge number of items, it is only used to describe the amount of things that are very, very small. • 1 mole (6.02x1023) of water molecules would barely fill a shot glass

  6. 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.

  7. 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

  8. The Mole • 1 dozen cookies = 12 cookies • 1 mole of cookies = 6.02 X 1023 cookies • 1 dozen cars = 12 cars • 1 mole of cars = 6.02 X 1023 cars • 1 dozen Al atoms = 12 Al atoms • 1 mole of Al atoms = 6.02 X 1023 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?)

  9. A Mole of ParticlesContains 6.02 x 1023 particles 1 mole C 1 mole H2O 1 mole NaCl = 6.02 x 1023 C atoms = 6.02 x 1023H2O molecules = 6.02 x 1023NaCl “molecules” (technically, ionics are compounds not molecules so they are called formula units) 6.02 x 1023 Na+ ions and 6.02 x 1023Cl– ions

  10. Avogadro’s Number as Conversion Factor 6.02 x 1023 particles 1 mole or 1 mole 6.02 x 1023 particles Note that a particle could be an atom OR a molecule!

  11. Using the mole in calculations #7 If you have a 35.67g piece of Chromium metal on your car, how many atoms of Chromium are in this piece of metal? • You are given mass and asked fornumber of particles • Let’s get some strategy

  12. Learning Check 1. Number of atoms in 0.500 mole of Al a) 500 Al atoms b) 6.02 x 1023 Al atoms c) 3.01 x 1023 Alatoms 2.Number of moles of S in 1.8 x 1024 S atoms a) 1.0 mole S atoms b) 3.0 mole S atoms c) 1.1 x 1048 mole S atoms

  13. Do you know how to measure out 3 moles of sugar or salt or water? • The mole is a counting unit, so we would have to count out 6.02x1023 particles of each substance. (no thank you) • There are 2 ways we can use to measure out a number of moles of a substance. • Measure it in grams (a mass) • Or measure it in liters (a volume) How we measure moles…

  14. Using mass to measure moles… • One of the units we can use to measure out a particular amount of moles is to weigh it out in grams? • The only problem with this method is that 1 mol of books will weigh more than 1 mol of pencils, since each book is heavier. • What if 1 mol of pencils weighs 500Gtons and 1 mol of books weighs 1x106Gtons. • How much would 3.0 mols of pencils and 3 mols of books weigh? • 500 Gtons * 3 mols = 1500 Gtons pencils • 1x106 Gtons * 3 mols = 3x106 Gtons

  15. Using mass to measure moles… • To be able to measure out 1 mol of a substance we would need access to the known mass in grams of 1 mol of any substance in question • We would need a data table that provided all of these masses since every substance involved would have its own mass. • Remember, we don’t use the mole to count anything but atoms, molecules, etc. • So we need a table that provides the mass 1 mole would weigh for every combination of atoms known to man.

  16. Molar Mass • 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

  17. 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 termswhich mean the SAME NUMBER… just different units

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

  19. Molar Mass of Molecules and Compounds Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole of CaCl2 = 111.1 g/mol 1 mole Ca x 40.1 g/mol + 2 moles Cl x 35.5 g/mol = 111.1 g/mol CaCl2 1 mole of N2O4 = 92.0 g/mol

  20. Learning Check! • Molar Mass of K2O = ? Grams/mole B. MolarMass of antacid Al(OH)3 = ? Grams/mole

  21. Calculations with Molar Mass molar mass Grams Moles

  22. Converting 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

  23. 1 mole of any gas at STP has volume 22.4L STP: STANDARD TEMPERATURE AND PRESSURE = 0C and 101.3 KPa molar volume Volume Moles Calculations with Molar Volume

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

  25. Learning Check! The artificial sweetener aspartame (Nutra-Sweet) formula C14H18N2O5 is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame?

  26. Atoms/Molecules and Grams • Since 6.02 X 1023 particles = 1 mole AND1 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!

  27. Using the mole in calculations #7 If you have a 35.67g piece of Chromium metal on your car, how many atoms of Chromium are in this piece of metal? • You are given mass and asked fornumber of particles • Let’s get some strategy

  28. Volume of Gas at STP Volume of Gas at STP Representative Particles Representative Particles 1 mole Mole Mole 1 mole 1 mole 22.4 L 22.4 L 23 23 6.02x10 6.02x10 atomic 22.4 L 22.4 L 1 mole 1 mole 1 mole mass 23 23 atomic atomic 1 mole 1 mole 6.02x10 6.02x10 mass mass 1 mole We are given a mass Mass Mass 1 mole atomic 1 mole mass 1 mole

  29. Calculations molar mass Avogadro’s numberGrams Moles particles Everything must go through Moles!!!

  30. 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 1023 atoms Cu 63.5 g Cu 1 mol Cu = 3.4 X 1023 atoms Cu

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

  32. Learning Check! What is the mass (in grams) of 1.20 X 1024 molecules of glucose (C6H12O6)?

  33. Learning Check! How many atoms of O are present in 78.1 g of oxygen? 78.1 g O2 1 mol O2 6.02 X 1023molecules O2 2 atoms O 32.0 g O2 1 mol O2 1 molecule O2

  34. Percent Composition What is the percent carbon in C5H8NO4 (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

  35. 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). NO2 2 atoms of O for every 1 atom of N 1 mole of NO2 : 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.

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

  37. 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. • 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

  38. 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 moles of O = 5.34 g = 0.334 moles of O 16.00 g/mole Formula: (HONORS only)

  39. Calculation of the Molecular Formula(HONORS only) A compound has an empirical formula of NO2. The colourless liquid, used in rocket engines has a molar mass of 92.0 g/mole. What is the molecular formula of this substance?

  40. 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

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