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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, X (in scientific notation) Amedeo _________ (1776 – 1856)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

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

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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) How many rapps contain 40 gummy bears? a) 5b) 10c) 20 Learning Check

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How does the Avogradro number come from? 1 Hydrogen contains only one proton One proton weighs 0,166x10^-23 grams 1 gram contains 1/Hydrogen Mass atoms Therefore 1 gram contains 1/(0,166x10^-23) atoms= 6,02x10^23 This calculation is the same for every substance And how many atoms are present in 4 gram of Helium? 4/4*1.66 x =6.02*10 23 Each nucleon weighs 1.66 x therefore for each element, defined x the atomic mass of the element in x grams there are 6.02*10 23 molecules. It is always the same ratio.

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6.023 x that many 602,300,000,000,000,000,000,000

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= 6.02 x C atoms = 6.02 x H 2 O molecules = 6.02 x NaCl “molecules” (technically, ionics are compounds not molecules so they are called formula units) 6.02 x Na + ions and 6.02 x Cl – ions A Mole of Particles A Mole of Particles Contains 6.02 x particles 1 mole C 1 mole H 2 O 1 mole NaCl

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

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Na Q: If ONE Sodium atom weighs daltons, how many Sodium atoms would it take to weigh grams ?

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What does one Mole of Lithium atoms weigh ? What does one Mole of Carbon atoms weigh ? What does one Mole of Water molecules weigh ? What does one Mole of O 2 molecules weigh ?

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Molar mass The mass of one mole is called “molar mass” E.g. 1 mol Li = 6.94 g Li This is expressed as 6.94 g/mol What are the following molar masses? SSO 2 Cu 3 (BO 3 ) g/mol g/mol g/mol Calculate molar masses (to 2 decimal places) CaCl 2 (NH 4 ) 2 CO 3 O 2 Pb 3 (PO 4 ) 2 C 6 H 12 O 6 Cux 3 = x 3= Bx 2 = x 2= Ox 6 = x 6=

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Converting between grams and moles If we are given the # of grams of a compound we can determine the # of moles, & vise-versa In order to convert from one to the other you must first calculate molar mass g = mol x g/mol mol = g g/mol This can be represented in an “ equation triangle ” g mo l g/mo l g= g/mol x mol0.25HCl 53.15H 2 SO NaCl 1.27Cu Equationmol (n)gg/molFormula mol= g g/mol g= g/mol x mol mol= g g/mol

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

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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 Molar Mass

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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

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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 = g/mole

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Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole of CaCl 2 = g/mol 1 mole Ca x 40.1 g/mol + 2 moles Cl x 35.5 g/mol = g/mol CaCl 2 1 mole of N 2 O 4 = 92.0 g/mol Molar Mass of Molecules and Compounds

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

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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

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molar mass Grams Moles Calculations with Molar Mass

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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

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1. Molar mass of Al1 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

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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!

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Atoms/Molecules and Grams Since 6.02 X 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 through MOLES.

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

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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 atoms Cu 63.5 g Cu 1 mol Cu = 3.4 X atoms Cu

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

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

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

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What is stoichiometry? Stoichiometry is the quantitative study of reactants and products in a chemical reaction.

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Ag + Cl 2 AgCl 1211 Both sides must be equal for ALL atoms

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