Slide 1 of 41 Chemistry 12.2

© Copyright Pearson Prentice Hall Slide 2 of 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.

© Copyright Pearson Prentice Hall Chemical Calculations > Slide 3 of 41 Writing and Using Mole Ratios How are mole ratios used in chemical calculations? 12.2

© Copyright Pearson Prentice Hall Slide 4 of 41 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. 12.2

Slide 5 of 41 © Copyright Pearson Prentice Hall 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. 12.2

Slide 6 of 41 © Copyright Pearson Prentice Hall 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. 12.2

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© Copyright Pearson Prentice Hall Slide 11 of 41 Practice Problems for Sample Problem 12.2 Problem Solving Solve Problem 12 with the help of an interactive guided tutorial.

Slide 12 of 41 © Copyright Pearson Prentice Hall Chemical Calculations > Writing and Using Mole Ratios Mass-Mass Calculations 12.2

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© Copyright Pearson Prentice Hall Slide 17 of 41 Practice Problems for Sample Problem 12.3 Problem Solving Solve Problem 13 with the help of an interactive guided tutorial. `

© Copyright Pearson Prentice Hall Chemical Calculations > Slide 18 of 41 Other Stoichiometric Calculations What is the general procedure for solving a stoichiometric problem? 12.2

Slide 19 of 41 © Copyright Pearson Prentice Hall 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. 12.2

© Copyright Pearson Prentice Hall Slide 20 of 41 Chemical Calculations > Other Stoichiometric Calculations Solution Diagram 12.2

© Copyright Pearson Prentice Hall Slide 21 of 41 Chemical Calculations > Other Stoichiometric Calculations Problem-Solving Approach 12.2

© Copyright Pearson Prentice Hall Slide 22 of 41 Chemical Calculations > Other Stoichiometric Calculations Simulation 13 Strengthen your analytical skills by solving stoichiometric problems.

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© Copyright Pearson Prentice Hall Slide 27 of 41 Practice Problems for Sample Problem 12.4 Problem Solving Solve Problem 15 with the help of an interactive guided tutorial.

© Copyright Pearson Prentice Hall Slide 28 of 41 Section Quiz -or- Continue to: Launch: Assess students’ understanding of the concepts in Section 12.2 Section Quiz

© Copyright Pearson Prentice Hall Slide 29 of Section Quiz. 1.How many moles of water are produced when 2.5 mol of O 2 react according to the following equation? C 3 H 8 + 5O 2  3CO 2 + 4H 2 O a.2.0 b.2.5 c.3.0 d.4.0

© Copyright Pearson Prentice Hall Slide 30 of 41 2.Nitrogen gas reacts with hydrogen gas to produce ammonia gas. N 2 (g) + 3H 2 (g)  2NH 3 (g) What volume of H 2 is required to react with 3.00 L of N 2, and what volume of NH 3 is produced at 200°C? a.volume of H 2 = 9.00 L, volume of NH 3 = 6.00 L b.volume of H 2 = 3.00 L, volume of NH 3 = 3.00 L c.volume of H 2 = 3.00 L, volume of NH 3 = 6.00 L d.volume of H 2 = 1.00 L, volume of NH 3 = 1.50 L 12.2 Section Quiz

© Copyright Pearson Prentice Hall Slide 31 of 41 3.Automotive airbags inflate when sodium azide, NaN 3, rapidly decomposes to its component elements via this reaction: 2NaN 3  2Na + 3N 2. How many grams of sodium azide are required to form 5.00 g of nitrogen gas? a g b g c.7.74 g d.1.36 g 12.2 Section Quiz

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