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 mass (in grams) of 5.4 moles of H2O? Do Now What is the mass (in grams) of 5.4 moles of H2O? How many molecules of CH4 are in 6 moles of CH4? How many moles of O2 molecules are in 44.8 L of O2 at STP? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

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. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Combustion of Gasoline 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) http://www3.epa.gov/climatechange/kids/ Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

2H2(g) + O2(g) ↔ 2H2O(l) ∆H = -482 kJ 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? http://energy.gov/eere/videos/energy-101-fuel-cell-technology Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Writing and Using Mole Ratios Mass-Mass Calculations N2(g) + 3H2(g)  2NH3(g) If I want to produce 150 grams of NH3, how many grams of hydrogen will I need? 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.

Calculating the Mass of a Product Sample Problem 12.4 Calculating the Mass of a Product Calculate the number of grams of NH3 produced by the reaction of 5.40 g of hydrogen with an excess of nitrogen. The balanced equation is: N2(g) + 3H2(g)  2NH3(g) Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Change given unit to moles Sample Problem 12.4  2 mol NH3 3 mol H2 5.40 g H2  1 mol H2 2.0 g H2 17.0 g NH3 1 mol NH3 Given quantity Change given unit to moles Mole ratio Change moles to grams = 31 g NH3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.