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12.1 The Arithmetic of Equations > Chapter 12 Stoichiometry 12.1 The Arithmetic of Equations 12.2 Chemical Calculations 12.3 Limiting Reagent and Percent Yield 1 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 12.1 The Arithmetic of Equations > Using Equations Do Now: Ammonia, NH3, is one of the most highly produced inorganic chemicals. It is used for fertilizing crops and to produce plastics, fibers, explosives, nitric acid, dyes, and pharmaceuticals. Balance the equation for producing ammonia. __N2(g) + __H2(g) __NH3(g) 2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 12.1 The Arithmetic of Equations > Using Equations Do Now: Ammonia, NH3, is one of the most highly produced inorganic chemicals. It is used for fertilizing crops and to produce plastics, fibers, explosives, nitric acid, dyes, and pharmaceuticals. Balance the equation for producing ammonia. N2(g) + 3H2(g) 2NH3(g) 3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 12.1 The Arithmetic of Equations > Using Equations Stoichiometry Calculation of quantities of reactants and products in chemical reactions From the Greek words stoicheion – element metron - measure 4 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 12.1 The Arithmetic of Equations > Chemical Equations Balanced equations can be interpreted in terms of • numbers of atoms, molecules, or moles • mass • volume 5 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 12.1 The Arithmetic of Equations > Chemical Equations N2(g) + 3H2(g) 2NH3(g) + 1 2 atoms N + 6 atoms H 2 atoms N and 6 atoms H 1 molecule N2 + 3 molecules H2 2 molecules NH3 10 molecules N2 + 30 molecules H2 20 molecules NH3 ( 6.02 1023 molecules N2 ) 3 ( ) 2 ( 6.02 1023 molecules NH2 1 mol N2 + 3 mol H2 2 mol NH3 28 g N2 + 3 2 g H2 2 17 g NH3 34 g reactants 34 g products Assume STP 22.4 L 22.4 L N2 6 + 6.02 1023 molecules H2 + 22.4 L 22.4 L 67.2 L H2 22.4 L 22.4 L ) 22.4 L 44.8 L NH3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 12.1 The Arithmetic of Equations > Chemical Equations • MASS & ATOMS are conserved in EVERY chemical reaction • Molecules, formula units, moles, and volumes are not necessarily conserved— although they may be. 7 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 12.1 The Arithmetic of Equations > Chemical Equations Combustion of Methane CH4(g) + 2O2(g) CO2(g) + H2O(g) 8 ∆H = -810 kJ Interpret this equation in terms of - moles of reactants and products - mass of reactants and products - volume at STP of reactants and products Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 12.2 Chemical Calculations > Writing and Using Mole Ratios mole ratio: a conversion factor derived from the coefficients of a balanced chemical equation interpreted in terms of moles 9 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 12.2 Chemical Calculations > Writing and Using Mole Ratios In chemical calculations, mole ratios are used to convert between a given number of moles of a reactant or product to moles of a different reactant or product. 10 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 12.2 Chemical Calculations > Writing and Using Mole Ratios N2(g) + 3H2(g) 2NH3(g) The three mole ratios derived from the balanced equation above are: 1 mol N2 3 mol H2 11 2 mol NH3 1 mol N2 3 mol H2 2 mol NH3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 12.2 Chemical Calculations > Sample Problem 12.3 Calculating Moles of a Product How many moles of NH3 are produced when 0.60 mol of nitrogen reacts with hydrogen? 12 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 12.2 Chemical Calculations > Sample Problem 12.3 Multiply the given quantity of N2 by the mole ratio in order to find the moles of NH3. 0.60 mol N2 13 2 mol NH3 1 mol N2 = 1.2 mol NH3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 12.1 The Arithmetic of Equations > Chemical Equations Combustion of Gasoline 2C8H18 + 25O2 16CO2 + 18H2O ∆H = -10,224 kJ How many moles of CO2 will be produced from the combustion of 30 moles of C8H18? (note: 30 moles C8H18 is ~ 1 gallon of gasoline) 14 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 12.1 The Arithmetic of Equations > Chemical Equations Combustion of Hydrogen / Electrolysis 2H2(g) + O2(g) ↔ 2H2O(l) ∆H = -482 kJ How many moles of O2 are required to react with 10 moles of H2? 15 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 12.1 The Arithmetic of Equations > END OF 12.1 16 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.