Chapter 12 Stoichiometry 12.2 Chemical Calculations 12.1 The Arithmetic of Equations 12.2 Chemical Calculations 12.3 Limiting Reagent and Percent Yield Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

What is the mole ratio of Fe2O3 to Fe? Do Now 4Fe + 3O2  2Fe2O3 What is the mole ratio of Fe2O3 to Fe? What is the mole ratio of Fe2O3 to O2? How many moles of Fe2O3 will form from 8 moles of Fe in excess oxygen? If there are 127 moles of Fe, how many moles of Fe2O3 will form? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Writing and Using Mole Ratios Steps for Solving a Mass-Mass Problem Grams Known Moles Known Moles Unknown Grams Unknown Using Molar Mass Using Mole Ratios Using Molar Mass Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

What mass of phosphorus will be needed to produce 3.25 mol of P4O10? Phosphorus burns in air to produce a phosphorus oxide in the following reaction: 4P(s) + 5O2(g)  P4O10(s) What mass of phosphorus will be needed to produce 3.25 mol of P4O10? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

What mass of phosphorus will be needed to produce 3.25 mol of P4O10? Phosphorus burns in air to produce a phosphorus oxide in the following reaction: 4P(s) + 5O2(g)  P4O10(s) What mass of phosphorus will be needed to produce 3.25 mol of P4O10? 3.25 mol P4O10   = 403 g P 31.0 g P 1 mol P 1 mol P4O10 4 mol P Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

How many grams of carbon dioxide will be made when 100 grams of CH4 combusts with sufficient oxygen? CH4 + 2O2  CO2 + 2H2O Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

How many grams of carbon dioxide will be made when 100 grams of CH4 combusts with sufficient oxygen? CH4 + 2O2  CO2 + 2H2O 44 g CO2 1 mol CO2 100 g CH4  16.0 g CH4 1 mol CH4  = 275 g CO2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Other Stoichiometric Calculations The figure below summarizes the steps for a typical stoichiometric problem. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Calculating the Molecules of a Product Sample Problem 12.5 Calculating the Molecules of a Product How many molecules of oxygen are produced when 29.2 g of water is decomposed by electrolysis according to this balanced equation? 2H2O(l) 2H2(g) + O2(g) electricity Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

= 4.88  1023 molecules O2 Sample Problem 12.5 1 mol O2  2 mol H2O 29.2 g H2O  1 mol H2O 18.0 g H2O Given quantity Change to moles Mole ratio Change to molecules = 4.88  1023 molecules O2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Volume-Volume Stoichiometric Calculations Sample Problem 12.6 Volume-Volume Stoichiometric Calculations Nitrogen monoxide and oxygen gas combine to form the brown gas nitrogen dioxide, which contributes to photochemical smog. How many liters of nitrogen dioxide are produced when 34 L of oxygen react with an excess of nitrogen monoxide? Assume conditions are at STP. 2NO(g) + O2(g)  2NO2(g) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

34 L O2    1 mol O2 22.4 L O2 1 mol NO2 22.4 L NO2 2 mol NO2 Sample Problem 12.6 34 L O2    1 mol O2 22.4 L O2 1 mol NO2 22.4 L NO2 2 mol NO2 Given quantity Change to moles Mole ratio Change to liters = 68 L NO2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Finding the Volume of a Gas Needed for a Reaction Sample Problem 12.7 Finding the Volume of a Gas Needed for a Reaction Assuming STP, how many liters of oxygen are needed to produce 20.4 L SO3 according to this balanced equation? 2SO2(g) + O2(g)  2SO3(g) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Finding the Volume of a Gas Needed for a Reaction Sample Problem 12.7 Finding the Volume of a Gas Needed for a Reaction Assuming STP, how many liters of oxygen are needed to produce 20.4 L SO3 according to this balanced equation? 2SO2(g) + O2(g)  2SO3(g) 10.2 L O2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) Methane burns in air by the following reaction: CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) What volume of water vapor is produced at STP by burning 501 g of methane? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) Methane burns in air by the following reaction: CH4(g) + 2O2(g)  CO2(g) + 2H2O(g) What volume of water vapor is produced at STP by burning 501 g of methane? 22.4 L H2O 1 mol H2O 501 g CH4  16.05 g CH4 1 mol CH4  2 mol H2O = 1.40  103 L H2O Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.