Kinetics

6 Key excerpts on "Kinetics"

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  Chemistry

  Structure and Dynamics

  • James N. Spencer, George M. Bodner, Lyman H. Rickard(Authors)
  • 2011(Publication Date)
  • Wiley

    (Publisher)

  Under normal conditions, however, these reactions invariably stop at SO 2 because the reaction between SO 2 and O 2 to form SO 3 is extremely slow. To fully understand chemical reactions, we need to combine the predictions of thermodynamics with studies of the factors that influence the rates of chemical reactions. These factors fall under the general heading of chemical Kinetics (from a Greek stem meaning “to move”), which is the subject of this chapter. 2 H 2 S(g) + 3 O 2 (g) ¡ 2 H 2 O(g) + 2 SO 2 (g) CS 2 (g) + 3 O 2 (g) ¡ CO 2 (g) + 2 SO 2 (g) S 8 (s) + 8 O 2 (g) ¡ 8 SO 2 (g) ¢G° = - 406.77 kJ/mol rxn 2 K(s) + 2 H 2 O(l) ¡ 2 K + (aq) + 2 OH - (aq) + H 2 (g) Fe 2 O 3 (s) + 2 Al(s) ¡ Al 2 O 3 (s) + 2 Fe(s) 2 H 2 (g) + O 2 (g) ¡ 2 H 2 O(g) 14.1 THE FORCES THAT CONTROL A CHEMICAL REACTION 641 ➤ CHECKPOINT Thermodynamics predicts that under normal circumstances carbon in the form of graphite is more stable than carbon in the form of diamond. Why don’t you have to worry that a diamond ring will turn to graphite? The reaction between and powdered aluminum gives off so much energy it is called the thermite reaction. Fe 2 O 3 14.2 Chemical Kinetics Chemical Kinetics can be defined as the search for answers to the following questions. ● What is the rate at which the reactants are converted into the products of a reaction? ● What factors influence the rate of the reaction? ● What is the sequence of steps, or the mechanism, by which the reactants are converted into products? As we saw in Section 10.3, the term rate is used to describe the change in a quan- tity that occurs per unit of time. The rate at which cars are sold, for example, is equal to the number of cars that change hands divided by the period of time dur- ing which this number is counted. The rate at which an object travels through space is the distance traveled per unit of time, such as miles per hour or kilome- ters per second.

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  Chemistry

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

    (Publisher)

  In this chapter, we will examine the factors that Chapter 12 | Kinetics 651 influence the rates of chemical reactions, the mechanisms by which reactions proceed, and the quantitative techniques used to determine and describe the rate at which reactions occur. 12.1 Chemical Reaction Rates By the end of this section, you will be able to: • Define chemical reaction rate • Derive rate expressions from the balanced equation for a given chemical reaction • Calculate reaction rates from experimental data A rate is a measure of how some property varies with time. Speed is a familiar rate that expresses the distance traveled by an object in a given amount of time. Wage is a rate that represents the amount of money earned by a person working for a given amount of time. Likewise, the rate of a chemical reaction is a measure of how much reactant is consumed, or how much product is produced, by the reaction in a given amount of time. The rate of reaction is the change in the amount of a reactant or product per unit time. Reaction rates are therefore determined by measuring the time dependence of some property that can be related to reactant or product amounts. Rates of reactions that consume or produce gaseous substances, for example, are conveniently determined by measuring changes in volume or pressure. For reactions involving one or more colored substances, rates may be monitored via measurements of light absorption. For reactions involving aqueous electrolytes, rates may be measured via changes in a solution’s conductivity. For reactants and products in solution, their relative amounts (concentrations) are conveniently used for purposes of expressing reaction rates.

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  Chemistry: Atoms First

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

    (Publisher)

  So why do we not see diamond spontaneously forming graphite? The answer is found in the topic of this Chapter 17 | Kinetics 895 chapter, chemical Kinetics, which involves the rate at which reactions take place. It turns out that while the conversion of diamond into graphite is a spontaneous process, it occurs so slowly that we do not observe the conversion taking place on any time scale we know. The study of chemical Kinetics concerns the second and third questions—that is, the rate at which a reaction yields products and the molecular-scale means by which a reaction occurs. In this chapter, we will examine the factors that influence the rates of chemical reactions, the mechanisms by which reactions proceed, and the quantitative techniques used to determine and describe the rate at which reactions occur. 17.1 Chemical Reaction Rates By the end of this section, you will be able to: • Define chemical reaction rate • Derive rate expressions from the balanced equation for a given chemical reaction • Calculate reaction rates from experimental data A rate is a measure of how some property varies with time. Speed is a familiar rate that expresses the distance traveled by an object in a given amount of time. Wage is a rate that represents the amount of money earned by a person working for a given amount of time. Likewise, the rate of a chemical reaction is a measure of how much reactant is consumed, or how much product is produced, by the reaction in a given amount of time. The rate of reaction is the change in the amount of a reactant or product per unit time. Reaction rates are therefore determined by measuring the time dependence of some property that can be related to reactant or product amounts. Rates of reactions that consume or produce gaseous substances, for example, are conveniently determined by measuring changes in volume or pressure. For reactions involving one or more colored substances, rates may be monitored via measurements of light absorption.

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  Chemistry 2e

  • Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson(Authors)
  • 2019(Publication Date)
  • Openstax

    (Publisher)

  INTRODUCTION CHAPTER 12 Kinetics 12.1 Chemical Reaction Rates 12.2 Factors Affecting Reaction Rates 12.3 Rate Laws 12.4 Integrated Rate Laws 12.5 Collision Theory 12.6 Reaction Mechanisms 12.7 Catalysis The lizard in the photograph is not simply enjoying the sunshine or working on its tan. The heat from the sun’s rays is critical to the lizard’s survival. A warm lizard can move faster than a cold one because the chemical reactions that allow its muscles to move occur more rapidly at higher temperatures. A cold lizard is a slower lizard and an easier meal for predators. From baking a cake to determining the useful lifespan of a bridge, rates of chemical reactions play important roles in our understanding of processes that involve chemical changes. Two questions are typically posed when planning to carry out a chemical reaction. The first is: “Will the reaction produce the desired products in useful quantities?” The second question is: “How rapidly will the reaction occur?” A third question is often asked when investigating reactions in greater detail: “What specific molecular-level processes take place as the reaction occurs?” Knowing the answer to this question is of practical importance when the yield or rate of a reaction needs to be controlled. The study of chemical Kinetics concerns the second and third questions—that is, the rate at which a reaction yields products and the molecular-scale means by which a reaction occurs. This chapter examines the factors Figure 12.1 An agama lizard basks in the sun. As its body warms, the chemical reactions of its metabolism speed up. CHAPTER OUTLINE that influence the rates of chemical reactions, the mechanisms by which reactions proceed, and the quantitative techniques used to describe the rates at which reactions occur.

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  Chemistry: Atoms First 2e

  • Edward J. Neth, Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson(Authors)
  • 2019(Publication Date)
  • Openstax

    (Publisher)

  INTRODUCTION CHAPTER 17 Kinetics 17.1 Chemical Reaction Rates 17.2 Factors Affecting Reaction Rates 17.3 Rate Laws 17.4 Integrated Rate Laws 17.5 Collision Theory 17.6 Reaction Mechanisms 17.7 Catalysis The lizard in the photograph is not simply enjoying the sunshine or working on its tan. The heat from the sun’s rays is critical to the lizard’s survival. A warm lizard can move faster than a cold one because the chemical reactions that allow its muscles to move occur more rapidly at higher temperatures. A cold lizard is a slower lizard and an easier meal for predators. From baking a cake to determining the useful lifespan of a bridge, rates of chemical reactions play important roles in our understanding of processes that involve chemical changes. Two questions are typically posed when planning to carry out a chemical reaction. The first is: “Will the reaction produce the desired products in useful quantities?” The second question is: “How rapidly will the reaction occur?” A third question is often asked when investigating reactions in greater detail: “What specific molecular-level processes take place as the reaction occurs?” Knowing the answer to this question is of practical importance when the yield or rate of a reaction needs to be controlled. The study of chemical Kinetics concerns the second and third questions—that is, the rate at which a reaction yields products and the molecular-scale means by which a reaction occurs. This chapter examines the factors Figure 17.1 An agama lizard basks in the sun. As its body warms, the chemical reactions of its metabolism speed up. CHAPTER OUTLINE that influence the rates of chemical reactions, the mechanisms by which reactions proceed, and the quantitative techniques used to describe the rates at which reactions occur.

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  Chemistry

  The Molecular Nature of Matter

  • James E. Brady, Neil D. Jespersen, Alison Hyslop(Authors)
  • 2014(Publication Date)
  • Wiley

    (Publisher)

  Part of the converter has been cut away to reveal the porous ceramic material that serves as the support for the catalyst. Figure 13.20 | Catalysts are very important in the petroleum industry. (a) Catalytic cracking towers at an oil refinery. (b) A variety of catalysts are available as beads, powders, or in other forms for various refinery operations. Courtesy BASF Corporation 674 Chapter 13 | Chemical Kinetics | Summary Organized by Learning Objective Understand and use the five conditions that affect how rapidly chemicals react The speeds or rates of reactions are controlled by five factors: (1) the nature of the reactants, (2) the ability of the reactants to meet, (3) the concentrations of the reactants, (4) the temperature, and (5) the presence of catalysts. The rates of heterogeneous reactions are determined largely by the area of contact between the phases; the rates of homogeneous reactions are determined by the concentrations of the reactants. Determine, from experimental data, the relative rates at which reactants disappear and products appear, and the rate of reaction, which is independent of the substance monitored The rate is measured by monitoring the change in reactant or product concentrations with time: rate = ∆(concentration)∙∆(time) In any chemical reaction, the rates of formation of products and the rates of disappearance of reactants are related by the coeffi- cients of the balanced overall chemical equation. Use experimental initial rate data to determine rate laws The rate law for a reaction relates the reaction rate to the molar concentrations of the reactants. The rate is proportional to the product of the molar concentrations of the reactants, each raised to an appropriate power. These exponents must be determined by experiments. The proportionality constant, k, is called the rate constant. The sum of the exponents in the rate law is the order (or overall order) of the reaction.

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