Reacting Masses

9 Key excerpts on "Reacting Masses"

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  eBook - PDF

  Chemistry

  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)

  CHAPTER 5 5.1 Counting by Weighing 5.2 Atomic Masses 5.3 Learning to Solve Problems 5.4 The Mole 5.5 Molar Mass 5.6 Percent Composition of Compounds 5.7 Determining the Formula of a Compound 5.8 Chemical Equations Chemical Reactions The Meaning of a Chemical Equation 5.9 Balancing Chemical Equations 5.10 Stoichiometric Calculations: Amounts of Reactants and Products 5.11 The Concept of Limiting Reactant A. Determination of Limiting Reactant Using Reactant Quantities B. Determination of Limiting Reactant Using Quantities of Products Formed Stoichiometry Fireworks provide a spectacular example of chemical reactions. (Nick Kwan/Pexels) 189 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. C hemical reactions have a profound effect on our lives. There are many examples: Food is converted to energy in the human body; nitrogen and hydrogen are com- bined to form ammonia, which is used as a fertilizer; fuels and plastics are produced from petroleum; the starch in plants is synthesized from carbon dioxide and water using energy from sunlight; human insulin is produced in laboratories by bacteria; cancer is induced in humans by substances from our environment; and so on, in a seemingly end- less list. The central activity of chemistry is to understand chemical changes such as these, and the study of reactions occupies a central place in this book. We will examine why reactions occur, how fast they occur, and which specific pathways they follow.

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  eBook - PDF

  Foundations of College Chemistry

  • Morris Hein, Susan Arena, Cary Willard(Authors)
  • 2016(Publication Date)
  • Wiley

    (Publisher)

  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. A Short Review Molar mass The sum of the atomic masses of all the atoms in an element or com- pound is called molar mass. The term molar mass also applies to the mass of a mole of any formula unit—atoms, molecules, or ions; it is the atomic mass of an atom or the sum of the atomic masses in a molecule or an ion (in grams). Relationship between molecule and mole. A molecule is the smallest unit of a molecular substance (e.g., Br 2 ), and a mole is Avogadro’s number (6.022 × 10 23 ) of molecules of that substance. A mole of bromine (Br 2 ) has the same number of mol- ecules as a mole of carbon dioxide, a mole of water, or a mole of any other molecu- lar substance. When we relate molecules to molar mass, 1 molar mass is equivalent to 1 mol, or 6.022 × 10 23 molecules. The term mole also refers to any chemical species. It represents a quantity (6.022 × 10 23 particles) and may be applied to atoms, ions, electrons, and formula units of nonmolecular substances. In other words, 1 mole = { 6.022 × 10 23 molecules 6.022 × 10 23 formula units 6.022 × 10 23 atoms 6.022 × 10 23 ions Other useful mole relationships are molar mass = grams of a substance number of moles of the substance molar mass = grams of a monatomic element number of moles of the element number of moles = number of molecules 6.022 × 10 23 molecules mole Balanced equations.

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  eBook - PDF

  Introduction to General, Organic, and Biochemistry

  • Morris Hein, Scott Pattison, Susan Arena, Leo R. Best(Authors)
  • 2014(Publication Date)
  • Wiley

    (Publisher)

  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. A Short Review Molar mass The sum of the atomic masses of all the atoms in an element or compound is called molar mass. The term molar mass also applies to the mass of a mole of any formula unit—atoms, molecules, or ions; it is the atomic mass of an atom or the sum of the atomic masses in a molecule or an ion (in grams). Relationship between molecule and mole A molecule is the smallest unit of a mo- lecular substance (e.g., Br 2 ), and a mole is Avogadro’s number (6.022 * 10 23 ) of molecules of that substance. A mole of bromine (Br 2 ) has the same number of molecules as a mole of carbon dioxide, a mole of water, or a mole of any other molecular substance. When we relate molecules to molar mass, 1 molar mass is equivalent to 1 mol, or 6.022 * 10 23 molecules. The term mole also refers to any chemical species. It represents a quantity (6.022 * 10 23 particles) and may be applied to atoms, ions, electrons, and formula units of nonmolecular substances. In other words, 1 mole = d 6.022 * 10 23 molecules 6.022 * 10 23 formula units 6.022 * 10 23 atoms 6.022 * 10 23 ions Other useful mole relationships are molar mass = grams of a substance number of moles of the substance molar mass = grams of a monatomic element number of moles of the element number of moles = number of molecules 6.022 * 10 23 molecules > mole Balanced equations When using chemical equations for calculations of mole–mass–volume relationships between reactants and products, the equations must be balanced. Remember: The number in front of a formula in a balanced chemical equation represents the number of moles of that substance in the chemical reaction.

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  Available until 4 Dec |Learn more

  Principles of Chemical Engineering Processes

  Material and Energy Balances, Second Edition

  • Nayef Ghasem, Redhouane Henda(Authors)
  • 2014(Publication Date)
  • CRC Press

    (Publisher)

  5

  Material Ba

  lances on Reactive Systems

  Chapter 4 dealt with material balances on single- and multiunit systems with no chemical reactions. Normally, reactor is at the heart of chemical processes. In this chapter, first the concepts of stoichiometry as it relates to the material balance are discussed. Then, the application of the reactor in reactive systems is formulated. Next, the different types of balances are described, namely, the element material balance method and the molecular species method. As a special application, material balance on combustion systems is thoroughly discussed.

  Learning Objectives

  1. Write a balanced chemical reaction and use stoichiometry to determine the corresponding amounts of participants in a reaction (Section 5.1 ).
  2. Understand the formulations of the material balance (Section 5.2 ).
  3. Write balance equations based on the extent of reaction (Section 5.3 ).
  4. Write balance equations involving atomic species (Section. 5.4 ).
  5. Write balance equations using molecular species (Section 5.5 ).
  6. Use of the extent of reaction for a system of chemical reactions (Section 5.6 ).
  7. Use of component balance for a system of chemical reactions (Section 5.7 ).
  8. Apply the degrees of freedom analysis for a reactive system (Section 5.8 ) .
  9. Define the features of combustion processes and properly apply material balances on them (Section 5.9 ) .

  5.1 Stoichiometry Basics

  In the following, reaction stoichiometry is addressed in light of a few concepts that include the stoichiometric equation, stoichiometric coefficients, and stoichiometric ratios [1 ] .

  5.1.1 Stoichiometric Equation

  It is an equation that relates the relative number of molecules or moles of participants (reactants and products) in a chemical reaction. To be valid, the equation must be balanced. For example, the following stoichiometric equation is not balanced:

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  eBook - ePub

  General Chemistry for Engineers

  • Jeffrey Gaffney, Nancy Marley(Authors)
  • 2017(Publication Date)
  • Elsevier

    (Publisher)

  Chapter 4

  Chemical Equations and Mass Balance

  Abstract

  This chapter introduces stoichiometry beginning with the mole concept and using Avogadro’s number as a conversion factor between the number of moles and the number of fundamental units in a substance. Case studies are used to present the determination of the empirical and molecular formulas from experimental data. Methods for balancing chemical equations and determining the limiting reactant are covered. The difference between percent yield and atom economy in chemical reactions is discussed in terms of determining the most economical and greener processes, using the steel industry as a Case Study. The process controlling the aqueous solubility of ionic compounds and their influences on precipitation reactions is discussed. The determination of the concentration of aqueous solutions in molarity is also covered.

  Keywords

  Mole; Empirical formula; Chemical equations; Stoichiometry; Limiting reactant; Percent yield; Spectator ions; Solubility; Precipitation reactions; Molarity

  Outline

  4.1  

  The Mole

  4.2  

  The Empirical Formula

  4.3  

  Chemical Equations

  4.4  

  Stoichiometry

  4.5  

  Limiting Reactant and Percent Yield

  4.6  

  Aqueous Solubility of Ionic Compounds

  4.7  

  Precipitation Reactions in Aqueous Solution

  4.8  

  Concentrations in Aqueous Solution

  Study Questions

  Problems

  4.1 The Mole

  Since chemistry deals with the properties of individual atoms and molecules and how these atoms form chemical bonds to create compounds, it is important for chemists to determine the amount of a substance on the molecular scale. Although the common use of the term “amount of substance” used in Engineering may be interpreted as the weight (in grams) or the volume (in cm3 ) of a substance, in chemistry the amount of a substance is a measure of the number of fundamental particles, such as atoms, molecules, or ions that are present in a given mass of substance. The SI base unit for the amount of a substance is the mole . The exact definition of a mole is the mass of any substance, which contains the same number of fundamental units as there are atoms in exactly 12.000 g of 12 C. Carbon-12 was chosen to serve as the reference standard of the mole unit for the International System of Units since it was also chosen to serve as the reference standard for atomic mass and the atomic mass unit, as described in Chapter 1

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  eBook - PDF

  Chemistry

  • Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson(Authors)
  • 2015(Publication Date)
  • Openstax

    (Publisher)

  Figure 4.11 Airbags deploy upon impact to minimize serious injuries to passengers. (credit: Jon Seidman) 4.4 Reaction Yields 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 4.12): 1 slice of cheese + 2 slices of bread ⟶ 1 sandwich Stoichiometric amounts of sandwich ingredients for this recipe are bread and cheese slices in a 2:1 ratio. Provided with 28 slices of bread and 11 slices of cheese, one may prepare 11 sandwiches per the provided recipe, using all the provided cheese and having six slices of bread left over. In this scenario, the number of sandwiches prepared has been limited by the number of cheese slices, and the bread slices have been provided in excess. 198 Chapter 4 | Stoichiometry of Chemical Reactions This OpenStax book is available for free at http://cnx.org/content/col11760/1.9 Figure 4.12 Sandwich making can illustrate the concepts of limiting and excess reactants. Consider this concept now with regard to a chemical process, the reaction of hydrogen with chlorine to yield hydrogen chloride: H 2 (s) + Cl 2 (g) ⟶ 2HCl(g) The balanced equation shows the hydrogen and chlorine react in a 1:1 stoichiometric ratio.

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  eBook - PDF

  Chemistry: Atoms First

  • William R. Robinson, Edward J. Neth, Paul Flowers, Klaus Theopold, Richard Langley(Authors)
  • 2016(Publication Date)
  • Openstax

    (Publisher)

  Figure 7.11 Airbags deploy upon impact to minimize serious injuries to passengers. (credit: Jon Seidman) 7.4 Reaction Yields 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 7.12): 1 slice of cheese + 2 slices of bread ⟶ 1 sandwich Stoichiometric amounts of sandwich ingredients for this recipe are bread and cheese slices in a 2:1 ratio. Provided with 28 slices of bread and 11 slices of cheese, one may prepare 11 sandwiches per the provided recipe, using all the provided cheese and having six slices of bread left over. In this scenario, the number of sandwiches prepared has been limited by the number of cheese slices, and the bread slices have been provided in excess. 366 Chapter 7 | Stoichiometry of Chemical Reactions This OpenStax book is available for free at http://cnx.org/content/col12012/1.7 Figure 7.12 Sandwich making can illustrate the concepts of limiting and excess reactants. Consider this concept now with regard to a chemical process, the reaction of hydrogen with chlorine to yield hydrogen chloride: H 2 (s) + Cl 2 (g) ⟶ 2HCl(g) The balanced equation shows the hydrogen and chlorine react in a 1:1 stoichiometric ratio.

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  eBook - PDF

  Chemical, Biochemical, and Engineering Thermodynamics

  • Stanley I. Sandler(Author)
  • 2017(Publication Date)
  • Wiley

    (Publisher)

  Here we will consider mass balances when there is only a single chemical reaction; in Chapter 8 and later chapters the more general case of sev- eral chemical reactions occurring simultaneously is considered. Also, we will write the mass balances using only the number of moles since the stoichiometry of chemical re- actions is usually written in terms of the number of moles of each species that undergoes chemical reaction rather than the mass of each species that reacts. Using the notation  ˙ N i  k for the rate at which moles of species i enter (if positive) or leave (if negative) in flow stream k, we have the differential or rate-of-change form of the mass balance on species i as Rate-of-change mass balance with chemical reaction on a molar basis dN i dt = K  k=1 ( ˙ N i ) k +  dN i dt  rxn (2.3-1) where the last term is new and describes the rate at which species i is produced (if pos- itive) or consumed (if negative) within the system by chemical reaction. The difference form of this equation, obtained by integrating over the time period from t 1 to t 2 , is Difference form of the mass balance N i (t 2 ) − N i (t 1 ) = K  k=1 ⎧ ⎭ t 2 t 1 (N i ) k dt + (ΔN i ) rxn = K  k=1 ΔN k + (ΔN i ) rxn (2.3-2) where the summation terms after the equal signs are the changes in the number of moles of the species due to the flow streams, and the second terms are the result of the chemical reaction. Note that only if the flow rate of a stream is steady (i.e.,  ˙ N i  k is constant), then If a flow rate is steady (ΔN i ) k =  ˙ N i  k t 36 Chapter 2: Conservation of Mass Now consider the mass (mole) balances for a reactor in which the following chemical reaction occurs C 2 H 4 + Cl 2 → C 2 H 4 Cl 2 but in which neither ethylene nor chlorine is completely consumed.

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  eBook - PDF

  Chemistry

  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 .

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