<p>Unit 4: Reactions and Stoichiometry Content Outline: Basic Stoichiometry (4.3)</p><p>I. Stoichiometry (“Stoich” means “element”; “metry” means “measure”… measuring elements.) A. This is the careful quantitative (numbers) analysis of substances involved in chemical reactions. B. There are 2 basic types of stoichiometry problems: 1. Composition Stoichiometry a. This type deals with the mass relationships of elements in compounds. 2. Reaction Stoichiometry a. This type deals with the mass relationships between reactants and products in chemical reactions. b. To solve these problems, you must start with a correctly balanced chemical reaction equation. i. This tells you the relative number of moles (coefficients) for each reactant & products.</p><p>II. Review of Calculating Atomic Mass & Molar Mass for a compound: A. How to calculate a mole: 1. Determine the total atomic or molecular mass of the substance you are working with, using the chemical formula and Periodic Table. (Remember, how to find the Atomic Mass? – Hint… subscript.) 2. Then weigh out, using an electronic balance and weigh boat, that calculated amount. 3. Congratulations, you have just weighed out 1 mole of that substance!</p><p>For example: Atomic Mass Aluminum has an atomic mass of 26.98 AMUs. So you would weigh out 26.98 grams of Aluminum to get a workable amount called a mole. </p><p>Molecular Mass Salt (NaCl) has an atomic mass of: Sodium – 23.00 AMUs Chlorine – 35.5 AMUs Total AMUs = 23.00 + 35.5 = 17.00 AMUs Weigh out 58.5 grams of salt.</p><p>4. The unit for of measurement is g/mol.</p><p>III. Basic Measurements or Unit Conversions involving the Mole concept: A. More than a mole: the basic concept is amount you have/ amount of a mole = # of moles. You have 21.6 grams of Boron (B). How many moles do you have? 1 mole of Boron = 10.8 grams so… 21.6/10.8 = 2.0 moles.</p><p>B. Less than a mole: the basic concept is amount you have/ amount of a mole = # of moles. You have 16.03 grams of Sulfur (S). How many moles do you have? 1 mole of Sulfur = 32.06 grams so… 16.03/32.06 = 0.5 moles</p><p>C. Conversions from one unit to another unit involving the mole concept: </p><p> the basic concept is: Unit given x Unit wanted = Unit wanted (Follow the colors.) Unit given</p><p>The given unit cancels out and leaves you with the unit wanted. 1. From # of Moles  To # of Atoms/Molecules a. You have 2.0 moles of Copper. How many atoms of Copper do you have?</p><p>1 mole = 6.022 x 1023 atoms so: 2 moles x 6.022 x 10 23 atoms = 12.044 x 1023 atoms 1 mole But using your rules for significant figures, it becomes 1.2044 x 1024 atoms.</p><p>2. # of Atoms/Molecules  To # of moles a. You have 1.806 x 1024 atoms of Zinc (Zn). How many moles of Zinc do you have? Step 1: Convert 1.806 x 1024 to 18.06 x 1023 (It must the Avogadro exponent of 23.)</p><p>Step 2: 18.06 x 1023 Atoms x 1 mole = 3 moles 6.022 x 1023 atoms</p><p>3. From Grams  To # of Moles a. You have 54.0 grams of Carbon (C). How many moles of Carbon do you have?</p><p>54.0 grams x 1 mole = 4.5 moles 12.0 grams</p><p>4. From # of Moles  To Grams a. You have 8.5 moles of Fluorine (F) gas. How grams of Fluorine do you have?</p><p>8.5 moles x 19.00 grams = 161.5 grams 1 mole</p><p>IV. Mole Ratio A. A conversion factor that relates the amounts, in moles, of any two substances involved in a chemical reaction. B. All Stoichiometry problems require a mol to mol (mol:mol)ratio be used to convert substance A information into substance B information. 1. This information is found in the substance coefficients; not the subscripts. 2. The Law of Conservation of Matter must be satisfied before you can begin to work the problem.</p><p>For example: 2Al2O3(l)  4Al(s) + 3O2(g)</p><p>You can compare: 2 mol/4 mol OR 4 mol/2 mol OR You can compare: 2mol/3 mol OR 3 mol/2 mol OR You can compare: 4 mol/3 mol OR 3 mol/4mol</p>