Chemistry 12.2 Slide 1 of 41 12.2 Chemical Calculations The effectiveness of car’s air bags is based on the rapid conversion of a small mass of sodium azide into a large volume of gas. The entire reaction occurs in less than a second. You will learn how to use a balanced chemical equation to calculate the amount of product formed in a chemical reaction. Slide 2 of 41 © Copyright Pearson Prentice Hall 12.2 Chemical Calculations > Writing and Using Mole Ratios Writing and Using Mole Ratios How are mole ratios used in chemical calculations? Slide 3 of 41 © Copyright Pearson Prentice Hall 12.2 Chemical Calculations > Writing and Using Mole Ratios In chemical calculations, mole ratios are used to convert between moles of reactant and moles of product, between moles of reactants, or between moles of products. Slide 4 of 41 © Copyright Pearson Prentice Hall 12.2 Chemical Calculations > Writing and Using Mole Ratios Mole-Mole Calculations A mole ratio is a conversion factor derived from the coefficients of a balanced chemical equation interpreted in terms of moles. Slide 5 of 41 © Copyright Pearson Prentice Hall 12.2 Chemical Calculations > Writing and Using Mole Ratios To determine the number of moles in a sample of a compound, first measure the mass of the sample. Then use the molar mass to calculate the number of moles in that mass. Slide 6 of 41 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 12.2 Slide 7 of 41 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 12.2 Slide 8 of 41 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 12.2 Slide 9 of 41 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 12.2 Slide 10 of 41 © Copyright Pearson Prentice Hall Practice Problems for Sample Problem 12.2 Problem Solving 12.12 Solve Problem 12 with the help of an interactive guided tutorial. Slide 11 of 41 © Copyright Pearson Prentice Hall 12.2 Chemical Calculations > Writing and Using Mole Ratios Mass-Mass Calculations Slide 12 of 41 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 12.3 Slide 13 of 41 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 12.3 Slide 14 of 41 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 12.3 Slide 15 of 41 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 12.3 Slide 16 of 41 © Copyright Pearson Prentice Hall Practice Problems for Sample Problem 12.3 ` Problem Solving 12.13 Solve Problem 13 with the help of an interactive guided tutorial. Slide 17 of 41 © Copyright Pearson Prentice Hall 12.2 Chemical Calculations > Other Stoichiometric Calculations Other Stoichiometric Calculations What is the general procedure for solving a stoichiometric problem? Slide 18 of 41 © Copyright Pearson Prentice Hall 12.2 Chemical Calculations > Other Stoichiometric Calculations In a typical stoichiometric problem, the given quantity is first converted to moles. Then the mole ratio from the balanced equation is used to calculate the number of moles of the wanted substance. Finally, the moles are converted to any other unit of measurement related to the unit mole, as the problem requires. Slide 19 of 41 © Copyright Pearson Prentice Hall 12.2 Chemical Calculations > Other Stoichiometric Calculations Solution Diagram Slide 20 of 41 © Copyright Pearson Prentice Hall 12.2 Chemical Calculations > Other Stoichiometric Calculations Problem-Solving Approach Slide 21 of 41 © Copyright Pearson Prentice Hall Chemical Calculations > Other Stoichiometric Calculations Simulation 13 Strengthen your analytical skills by solving stoichiometric problems. Slide 22 of 41 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 12.4 Slide 23 of 41 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 12.4 Slide 24 of 41 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 12.4 Slide 25 of 41 © Copyright Pearson Prentice Hall SAMPLE PROBLEM 12.4 Slide 26 of 41 © Copyright Pearson Prentice Hall Practice Problems for Sample Problem 12.4 Problem Solving 12.15 Solve Problem 15 with the help of an interactive guided tutorial. Slide 27 of 41 © Copyright Pearson Prentice Hall 12.2 Section Quiz. Assess students’ understanding of the concepts in Section 12.2. Continue to: -or- Launch: Section Quiz Slide 28 of 41 © Copyright Pearson Prentice Hall 12.2 Section Quiz. 1. How many moles of water are produced when 2.5 mol of O2 react according to the following equation? C3H8 + 5O2 3CO2 + 4H2O a. 2.0 b. 2.5 c. 3.0 d. 4.0 Slide 29 of 41 © Copyright Pearson Prentice Hall 12.2 Section Quiz 2. Nitrogen gas reacts with hydrogen gas to produce ammonia gas. N2(g) + 3H2(g) 2NH3(g) What volume of H2 is required to react with 3.00 L of N2, and what volume of NH3 is produced at 200°C? a. volume of H2 = 9.00 L, volume of NH3 = 6.00 L b. volume of H2 = 3.00 L, volume of NH3 = 3.00 L c. volume of H2 = 3.00 L, volume of NH3 = 6.00 L d. volume of H2 = 1.00 L, volume of NH3 = 1.50 L Slide 30 of 41 © Copyright Pearson Prentice Hall 12.2 Section Quiz 3. Automotive airbags inflate when sodium azide, NaN3, rapidly decomposes to its component elements via this reaction: 2NaN3 2Na + 3N2. How many grams of sodium azide are required to form 5.00 g of nitrogen gas? a. 11.61 g b. 17.41 g c. 7.74 g d. 1.36 g Slide 31 of 41 © Copyright Pearson Prentice Hall END OF SHOW