Chemistry 12.2

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Chemistry 12.2

© Copyright Pearson Prentice Hall

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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.


Chemical Calculations >

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Writing and Using Mole Ratios

Writing and Using Mole Ratios

How are mole ratios used in chemical calculations?

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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.

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Mole-Mole Calculations

A mole ratio is a conversion factor derived from the coefficients of a balanced chemical equation interpreted in terms of moles.

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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.

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SAMPLE PROBLEM

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Practice Problems for Sample Problem 12.2

Problem Solving 12.12 Solve Problem 12 with the help of an interactive guided tutorial.

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Mass-Mass Calculations

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Chemical Calculations >

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Other Stoichiometric Calculations

Other Stoichiometric Calculations

What is the general procedure for solving a stoichiometric problem?

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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.

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Solution Diagram

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Problem-Solving Approach

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Simulation 13

Strengthen your analytical skills by solving stoichiometric problems.


SAMPLE PROBLEM

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Problem-Solving 12.19 Solve Problem 19 with the help of an interactive guided tutorial.


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Section Quiz

-or-Continue to: Launch:

Assess students’ understanding of the concepts in Section

12.2 Section Quiz.

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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


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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

12.2 Section Quiz


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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

12.2 Section Quiz

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Chemistry 12.2