Chemistry
Stoichiometric Calculations
Stoichiometric calculations involve using the balanced chemical equation to determine the quantitative relationships between reactants and products in a chemical reaction. These calculations are used to find the amount of reactants needed, the amount of products formed, and to predict the outcome of a reaction. Stoichiometric calculations are fundamental in understanding and predicting chemical reactions.
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12 Key excerpts on "Stoichiometric Calculations"
eBook - PDF- Morris Hein, Susan Arena, Cary Willard(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
184 Calculations from Chemical Equations CHAPTER OUTLINE 9.1 Introduction to Stoichiometry 9.2 Mole–Mole Calculations 9.3 Mole–Mass Calculations 9.4 Mass–Mass Calculations 9.5 Limiting Reactant and Yield Calculations The old adage “waste not, want not” is appropriate in our daily life and in the laboratory. Determining correct amounts comes into play in almost all professions. A seamstress determines the amount of material, lining, and trim necessary to produce a gown for her client by relying on a pat- tern or her own experience to guide the selection. A carpet layer deter- mines the correct amount of carpet and padding necessary to recarpet a customer’s house by calculating the floor area. The IRS determines the correct deduction for federal income taxes from your paycheck based on your expected annual income. In chemistry, calculations from chemical equations are important too. These same calculations and amounts are used frequently in medi- cine and pharmacy. Accurate calculations of dose and accurate measure- ment of chemicals are required in order for a pharmacist or a nurse to dispense the correct dosage of medicine to her patients. CHAPTER 9 Pyrosky/iStock/Getty Images 9.1 Introduction to Stoichiometry 185 9.1 Introduction to Stoichiometry LEARNING OBJECTIVE: Define stoichiometry and describe the strategy required to solve problems based on chemical equations. We often need to calculate the amount of a substance that is either produced from, or needed to react with, a given quantity of another substance. The area of chemistry that deals with quantitative relationships among reactants and products is known as stoichiometry (stoy-- key-- ah-- meh-- tree). Solving problems in stoichiometry requires the use of moles in the form of mole-ratios. The chemist also finds it necessary to calculate amounts of products or reactants by using a balanced chemical equation.
eBook - PDF- Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson(Authors)
- 2019(Publication Date)
- Openstax(Publisher)
Numerous variations on the beginning and ending computational steps are possible depending upon what particular quantities are provided and sought (volumes, solution concentrations, and so forth). Regardless of the details, all these calculations share a common essential component: the use of stoichiometric factors derived from balanced chemical equations. Figure 4.11 provides a general outline of the various computational steps associated with many reaction stoichiometry calculations. FIGURE 4.11 The flowchart depicts the various computational steps involved in most reaction stoichiometry 184 4 • Stoichiometry of Chemical Reactions Access for free at openstax.org calculations. 4.4 Reaction Yields LEARNING OBJECTIVES By the end of this section, you will be able to: • Explain the concepts of theoretical yield and limiting reactants/reagents. • Derive the theoretical yield for a reaction under specified conditions. • Calculate the percent yield for a reaction. The relative amounts of reactants and products represented in a balanced chemical equation are often referred to as stoichiometric amounts. All the exercises of the preceding module involved stoichiometric amounts of reactants. For example, when calculating the amount of product generated from a given amount of reactant, it was assumed that any other reactants required were available in stoichiometric amounts (or greater). In this module, more realistic situations are considered, in which reactants are not present in stoichiometric amounts. Limiting Reactant Consider another food analogy, making grilled cheese sandwiches ( Figure 4.13): Stoichiometric amounts of sandwich ingredients for this recipe are bread and cheese slices in a 2:1 ratio. Chemistry in Everyday Life Airbags Airbags ( Figure 4.12) are a safety feature provided in most automobiles since the 1990s.
- Morris Hein, Scott Pattison, Susan Arena, Leo R. Best(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
12.1 • Properties of Gases 167 Corbis RF/Age Fotostock America, Inc. T he old adage “waste not, want not” is appropriate in our daily life and in the laboratory. Determining correct amounts comes into play in almost all professions. A seamstress determines the amount of material, lining, and trim necessary to produce a gown for her client by relying on a pattern or her own experience to guide the selection. A carpet layer de- termines the correct amount of carpet and padding necessary to recarpet a customer’s house by calculating the floor area. The IRS determines the correct deduction for federal income taxes from your paycheck based on your expected annual income. 9.1 Introduction to Stoichiometry 9.2 Mole–Mole Calculations 9.3 Mole–Mass Calculations 9.4 Mass–Mass Calculations 9.5 Limiting Reactant and Yield Calculations CALCULATIONS FROM CHEMICAL EQUATIONS C H A P T E R 9 Accurate calculations of dose and accurate measurement of chemicals are required in order for a pharmacist to dispense the correct dosage of medicine to her patients. C H A P T E R O U T L I N E 168 CHAPTER 9 • Calculations from Chemical Equations 9.1 INTRODUCTION TO STOICHIOMETRY Define stoichiometry and describe the strategy required to solve problems based on chemical equations. We often need to calculate the amount of a substance that is either produced from, or needed to react with, a given quantity of another substance. The area of chemistry that deals with quantitative relationships among reactants and products is known as stoichiometry (stoy-key-ah-meh-tree). Solving problems in stoichiometry requires the use of moles in the form of mole ratios. The chemist also finds it necessary to calculate amounts of products or reactants by using a balanced chemical equation. With these calculations, the chemist can control the amount of product by scaling the reaction up or down to fit the needs of the laboratory and can thereby minimize waste or excess materials formed during the reaction.
eBook - PDF- Morris Hein, Susan Arena, Cary Willard(Authors)
- 2016(Publication Date)
- Wiley(Publisher)
T he old adage “waste not, want not” is appropriate in our daily life and in the laboratory. Determining cor- rect amounts comes into play in almost all professions. A seamstress determines the amount of material, lining, and trim necessary to produce a gown for her client by rely- ing on a pattern or her own experience to guide the selec- tion. A carpet layer determines the correct amount of carpet and padding necessary to recarpet a customer’s house by calculating the floor area. The IRS determines the correct deduction for federal income taxes from your paycheck based on your expected annual income. In chemistry, calculations from chemical equations are important too. These same calculations and amounts are used frequently in medicine and pharmacy. Accurate calculations of dose and accurate measurement of chemicals are required in order for a pharmacist to dispense the correct dosage of medicine to her patients. Calculations from Chemical Equations Corbis RF/Age Fotostock America, Inc. 9 C H A P T E R O U T L I N E 9.1 Introduction to Stoichiometry 9.2 Mole–Mole Calculations 9.3 Mole–Mass Calculations 9.4 Mass–Mass Calculations 9.5 Limiting Reactant and Yield Calculations 176 CHAPTER 9 Calculations from Chemical Equationss 9.1 Introduction to Stoichiometry Define stoichiometry and describe the strategy required to solve problems based on chemical equations. We often need to calculate the amount of a substance that is either produced from, or need- ed to react with, a given quantity of another substance. The area of chemistry that deals with quantitative relationships among reactants and products is known as stoichiometry (stoy-key-ah-meh-tree). Solving problems in stoichiometry requires the use of moles in the form of mole ratios. The chemist also finds it necessary to calculate amounts of products or reactants by using a balanced chemical equation.
eBook - PDF- Gary D. Christian, Purnendu K. Dasgupta, Kevin A. Schug(Authors)
- 2020(Publication Date)
- Wiley(Publisher)
Chapter 4 Stoichiometric Calculations: THE WORKHORSE OF THE ANALYST KEY THINGS TO LEARN FROM THIS CHAPTER How to calculate molarities and moles (key Equations: 4.4, 4.5) How to express analytical results How to calculate weight and percent analyted from molarities, volumes, and reaction ratios (key Equations: 4.5, 4.17–4.20, 4.25) Weight relationships for gravimetric analysis (key Equation: 4.28) Analytical chemistry deals with measurements of analytes in solids and concentrations in solution, from which we calculate masses. Thus, we prepare solutions of known con- centrations that can be used to calibrate instruments or to titrate sample solutions. We calculate the mass of an analyte in a solution from its concentration and the volume. We calculate the mass of product expected from the mass of reactants. All of these calculations require a knowledge of stoichiometry, that is, the ratios in which chemi- cals react, from which we apply appropriate conversion factors to arrive at the desired calculated results. Stoichiometry deals with the ratios in which chemicals react. In this chapter we review the fundamental concepts of mass, moles, and equiva- lents; the ways in which analytical results may be expressed for solids and liquids; and the principles of volumetric analysis and how stoichiometric relationships are used in titrations to calculate the mass of analyte. 4.1 Review of the Fundamentals Quantitative analysis is based on a few fundamental atomic and molecular concepts, which we review below. You have undoubtedly been introduced to these in your general chemistry course, but we briefly review them here since they are so fundamental to quantitative calculations. The Basics: Atomic, Molecular, and Formula Weights The atomic weight for any element is the weight of a specified number of atoms of that element, and that number is the same from one element to another.
- Martha Mackin(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
TEN Calculations based on equations OVERVIEW In Chapter 9 you learned how to write and balance an equation starting from a verbal description of a chemical reaction. You also learned how to translate a balanced equation into words. In Chapter 10 you will learn how to use the balanced equation to predict the quantity of reactant needed or the quantity of products formed in the reaction. If the number of moles of one sub-stance in the equation is given, the number of moles of another substance can be calculated. Both of these substances may be reactants, both may be products, or one substance may be a reac-tant and the other a product. Since moles can be converted to grams, the calculations can involve mole-mole conversions, mole-mass(g) or mass(g)-mole conversions, or mass(g)-mass(g) conversions. Chapter 10 also tells how to determine the limiting reagent and how to calculate percent yield. ••Specifics** 1. Definitions for the following terms should be learned: stoichiometry actual yield mole-ratio theoretical yield reagent percent yield limiting reagent 2. General concepts that should be learned: Number of related textbook objective 10.1 a. Being able to translate a chemical equation into quantitative terms. 10.2 b. Understanding the mole ratio between the number of moles of each of two substances in the reaction. 10.6 c. Understanding the significance of a limiting reagent in determin-ing the maximum amount of product formed. 10.7 d. Understanding the difference between actual yield and theoretical yield in order to calculate percent yield. 193 194 Chapter Ten 3. Types of numerical exercises that should be mastered: CHAPTER 10 TOPICAL OUTLINE I. Problems based on balanced equations 10.1 Stoichiometry A. Stoichiometric Calculations are calculations of the quantities of elements or compounds involved in a chemical reaction. B. They are based on relationships between the number of moles of reactants and the number,of moles of products.
eBook - PDF- Gary D. Christian, Purnendu K. Dasgupta, Kevin A. Schug(Authors)
- 2013(Publication Date)
- Wiley(Publisher)
Chapter Five Stoichiometric Calculations: THE WORKHORSE OF THE ANALYST Learning Objectives WHAT ARE SOME OF THE KEY THINGS WE WILL LEARN FROM THIS CHAPTER? ● How to calculate molarities and moles (key equations: 5.4, 5.5), p. 152 ● How to express analytical results, p. 159 ● How to calculate weight and percent analyted from molarities, volumes, and reaction ratios (key equations: 5.5, 5.17–5.20, 5.25), pp. 152, 169, 171 ● Weight relationships for gravimetric analysis (key equation: 5.28), p. 181 Analytical chemistry deals with measurements of analytes in solids and concentrations in solution, from which we calculate masses. Thus, we prepare solutions of known concentrations that can be used to calibrate instruments or to titrate sample solutions. We calculate the mass of an analyte in a solution from its concentration and the volume. We calculate the mass of product expected from the mass of reactants. All of Stoichiometry deals with the ratios in which chemicals react. these calculations require a knowledge of stoichiometry, that is, the ratios in which chemicals react, from which we apply appropriate conversion factors to arrive at the desired calculated results. In this chapter we review the fundamental concepts of mass, moles, and equivalents; the ways in which analytical results may be expressed for solids and liquids; and the principles of volumetric analysis and how stoichiometric relationships are used in titrations to calculate the mass of analyte. 5.1 Review of the Fundamentals Quantitative analysis is based on a few fundamental atomic and molecular concepts, which we review below. You have undoubtedly been introduced to these in your general chemistry course, but we briefly review them here since they are so fundamental to quantitative calculations. THE BASICS: ATOMIC, MOLECULAR, AND FORMULA WEIGHTS The atomic weight for any element is the weight of a specified number of atoms of that element, and that number is the same from one element to another.
eBook - PDFChemistry
The Molecular Nature of Matter
- Neil D. Jespersen, Alison Hyslop(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
Equivalencies obtained from balanced equations (Section 3.5) The coefficients in balanced chemical equations give us relationships between all reactants and products that can be used in factor- label calculations. Mass-to-mass calculations using balanced chemical equations (Section 3.5) A logical sequence of conversions allows calculation of all components of a chemical reaction. See Figure 3.6. Limiting reactant calculations (Section 3.6) When the amounts of at least two reactants are given, one will be used up before the other and dictate the amont of products formed and the amount of excess reactant left over. Theoretical, actual, and percentage yields (Section 3.7) The theoretical yield is based on the limiting reactant whether stated, implied, or calculated. The actual yield must be determined by experiment, and the percentage yield relates the magnitude of the actual yield to the percentage yield. Percentage yield = actual mass by experiment theoretical mass by calculation Ž 100% Multi-step percentage yield (Section 3.7) Modern chemical synthesis often involves more than one distinct reaction or step. The overall percentage yield of a multi-step synthesis is Overall % yield = a % yield 1 100 Ž % yield 2 100 Ž ... b 100% 146 Chapter 3 | The Mole and Stoichiometry =WileyPLUS, an online teaching and learning solution. Note to instructors: Many of the end-of-chapter problems are available for assignment via the WileyPLUS system. www.wileyplus.com. Review Problems are presented in pairs separated by blue rules. Answers to problems whose numbers appear in blue are given in Appendix B. More challenging problems are marked with an asterisk .
eBook - PDFChemistry
An Atoms First Approach
- Steven Zumdahl, Susan Zumdahl, Donald J. DeCoste, , Steven Zumdahl, Steven Zumdahl, Susan Zumdahl, Donald J. DeCoste(Authors)
- 2020(Publication Date)
- Cengage Learning EMEA(Publisher)
ions 230 CHAPTER 5 Stoichiometry Copyright 2021 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Stoichiometry Calculations ❯ Amounts of reactants consumed and products formed can be determined from the balanced chemical equation ❯ The limiting reactant is the one consumed first, thus limiting the amount of product that can form Yield ❯ The theoretical yield is the maximum amount that can be produced from a given amount of the limiting reactant ❯ The actual yield, the amount of product actually obtained, is always less than the theoretical yield ❯ Percent yield 5 actual yield sgd theoretical yield sgd 3 100% 1. Explain the concept of “counting by weighing” using marbles as your example. 2. Atomic masses are relative masses. What does this mean? 3. The atomic mass of boron (B) is given in the periodic table as 10.81, yet no single atom of boron has a mass of 10.81 u. Explain. 4. What are three conversion factors and in what order would you use them to convert the mass of a compound into atoms of a particular element in that compound— for example, from 1.00 g aspirin (C 9 H 8 O 4 ) to number of hydrogen atoms in the 1.00-g sample? 5. Fig. 5.5 illustrates a schematic diagram of a combustion device used to analyze organic compounds. Given that a certain amount of a compound containing carbon, hydrogen, and oxygen is combusted in this device, explain how the data relating to the mass of CO 2 pro- duced and the mass of H 2 O produced can be manipu- lated to determine the empirical formula.
eBook - PDF- William R. Robinson, Edward J. Neth, Paul Flowers, Klaus Theopold, Richard Langley(Authors)
- 2016(Publication Date)
- Openstax(Publisher)
In this module, the use of balanced chemical equations for various stoichiometric applications is explored. The general approach to using stoichiometric relationships is similar in concept to the way people go about many common activities. Food preparation, for example, offers an appropriate comparison. A recipe for making eight pancakes calls for 1 cup pancake mix, 3 4 cup milk, and one egg. The “equation” representing the preparation of pancakes per this recipe is 1 cup mix + 3 4 cup milk + 1 egg ⟶ 8 pancakes If two dozen pancakes are needed for a big family breakfast, the ingredient amounts must be increased proportionally according to the amounts given in the recipe. For example, the number of eggs required to make 24 pancakes is 24 pancakes × 1 egg 8 pancakes = 3 eggs Balanced chemical equations are used in much the same fashion to determine the amount of one reactant required to react with a given amount of another reactant, or to yield a given amount of product, and so forth. The coefficients in the balanced equation are used to derive stoichiometric factors that permit computation of the desired quantity. To Chapter 7 | Stoichiometry of Chemical Reactions 361 illustrate this idea, consider the production of ammonia by reaction of hydrogen and nitrogen: N 2 (g) + 3H 2 (g) ⟶ 2NH 3 (g) This equation shows ammonia molecules are produced from hydrogen molecules in a 2:3 ratio, and stoichiometric factors may be derived using any amount (number) unit: 2 NH 3 molecules 3 H 2 molecules or 2 doz NH 3 molecules 3 doz H 2 molecules or 2 mol NH 3 molecules 3 mol H 2 molecules These stoichiometric factors can be used to compute the number of ammonia molecules produced from a given number of hydrogen molecules, or the number of hydrogen molecules required to produce a given number of ammonia molecules. Similar factors may be derived for any pair of substances in any chemical equation.
eBook - PDFChemistry
The Molecular Nature of Matter
- James E. Brady, Neil D. Jespersen, Alison Hyslop(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
Empirical formulas from percentage composition (Section 3.4) Percentage composition correlates information from different experiments, to determine empirical formulas. Balancing chemical equations (Section 3.5) Balancing equations involves writing the unbalanced equation and then adjusting the coefficients to get equal numbers of each kind of atom on both sides of the arrow. Equivalencies obtained from balanced equations (Section 3.5) The coefficients in balanced chemical equations give us relationships between all reactants and products that can be used in factor- label calculations. Mass-to-mass calculations using balanced chemical equations (Section 3.5) A logical sequence of conversions allows calculation of all components of a chemical reaction. See Figure 3.6. Tools for Problem Solving The following tools were introduced in this chapter. Study them carefully so you can select the appropriate tool when needed. 146 Chapter 3 | The Mole and Stoichiometry Limiting reactant calculations (Section 3.6) When the amounts of at least two reactants are given, one will be used up before the other and dictate the amont of products formed and the amount of excess reactant left over. Theoretical, actual, and percentage yields (Section 3.7) The theoretical yield is based on the limiting reactant whether stated, implied, or calculated. The actual yield must be determined by experiment, and the percentage yield relates the magnitude of the actual yield to the percentage yield. Percentage yield = actual mass by experiment theoretical mass by calculation Ž 100% Multi-step percentage yield (Section 3.7) Modern chemical synthesis often involves more than one distinct reaction or step. The overall percentage yield of a multi-step synthesis is Overall % yield = a % yield 1 100 Ž % yield 2 100 Ž ... b 100% Review Questions 147 =WileyPLUS, an online teaching and learning solution.
eBook - PDF- Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson(Authors)
- 2015(Publication Date)
- Openstax(Publisher)
In this module, the use of balanced chemical equations for various stoichiometric applications is explored. The general approach to using stoichiometric relationships is similar in concept to the way people go about many common activities. Food preparation, for example, offers an appropriate comparison. A recipe for making eight pancakes calls for 1 cup pancake mix, 3 4 cup milk, and one egg. The “equation” representing the preparation of pancakes per this recipe is 1 cup mix + 3 4 cup milk + 1 egg ⟶ 8 pancakes If two dozen pancakes are needed for a big family breakfast, the ingredient amounts must be increased proportionally according to the amounts given in the recipe. For example, the number of eggs required to make 24 pancakes is 24 pancakes × 1 egg 8 pancakes = 3 eggs Balanced chemical equations are used in much the same fashion to determine the amount of one reactant required to react with a given amount of another reactant, or to yield a given amount of product, and so forth. The coefficients in the balanced equation are used to derive stoichiometric factors that permit computation of the desired quantity. To Chapter 4 | Stoichiometry of Chemical Reactions 193 illustrate this idea, consider the production of ammonia by reaction of hydrogen and nitrogen: N 2 (g) + 3H 2 (g) ⟶ 2NH 3 (g) This equation shows ammonia molecules are produced from hydrogen molecules in a 2:3 ratio, and stoichiometric factors may be derived using any amount (number) unit: 2 NH 3 molecules 3 H 2 molecules or 2 doz NH 3 molecules 3 doz H 2 molecules or 2 mol NH 3 molecules 3 mol H 2 molecules These stoichiometric factors can be used to compute the number of ammonia molecules produced from a given number of hydrogen molecules, or the number of hydrogen molecules required to produce a given number of ammonia molecules. Similar factors may be derived for any pair of substances in any chemical equation.
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