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Chapter 13 Lecture Chapter 13 Chemical Kinetics © 2014 Pearson Education, Inc.  Chemical kinetics Chemical kinetics is the branch of chemistry concerned with the study of the rates of chemical reactions...

Chapter 13 Lecture Chapter 13 Chemical Kinetics © 2014 Pearson Education, Inc.  Chemical kinetics Chemical kinetics is the branch of chemistry concerned with the study of the rates of chemical reactions and the factors that influence those rates. It delves into understanding how and why reactions occur at certain speeds and how reaction rates can be altered. This field explores concepts such as reaction mechanisms, reaction rates, rate laws, and the effect of factors like temperature, concentration, and catalysts on reaction rates. Studying chemical kinetics is essential for understanding and controlling chemical reactions in various industries, from pharmaceuticals to environmental science. © 2014 Pearson Education, Inc.  Some branches of science to, which chemical kinetic is relevant Branch Application of kinetics Biology Physiological processes (e.g., digestion and metabolism) bacterial growth) Chemical engineering Reactor design, production process Electrochemistry Electrode processes Geology Flow processes Inorganic chemistry Inorganic reaction mechanism Mechanical Physical metallurgy, crystal dislocation mobility Engineering Organic chemistry Reaction mechanism Pharmacology Drug action, drug-drug interaction Physics Viscosity, diffusion , nuclear processes © 2014 Pearson Education, Inc.  Key concepts and aspects of chemical kinetics Reaction Rate: The rate of a chemical reaction is the change in the concentration of reactants or products per unit of time. Reaction Mechanism: This describes the step-by-step sequence of elementary reactions that make up an overall chemical reaction. Rate Laws: Rate laws are mathematical expressions that relate the rate of a reaction to the concentrations of reactants. These laws are determined experimentally Reaction Order: The reaction order with respect to a particular reactant indicates how the concentration of that reactant affects the reaction rate. It can be zero, first, second, or even fractional. Activation Energy: This is the minimum amount of energy that reactant molecules must possess to initiate a chemical reaction. © 2014 Pearson Education, Inc.  Chemical kinetics finds numerous applications in academic research. Reaction Mechanism Elucidation: helps researchers understand the step-by-step processes (reaction mechanisms). Catalyst Design and Optimization: Understanding the kinetics of catalytic reactions is essential for designing and optimizing catalysts for various industrial processes, such as in petroleum refining, environmental remediation, and chemical synthesis. Atmospheric Chemistry: Studying the kinetics of atmospheric reactions helps researchers understand the formation and depletion of pollutants, ozone layer depletion, and the dynamics of climate change. This knowledge is essential for developing strategies to mitigate air pollution and address global environmental challenges. Materials Science: Chemical kinetics is used to investigate the kinetics of phase transformations, such as crystallization, nucleation, and growth, in materials science. This knowledge is critical for designing and synthesizing advanced materials with tailored properties for various applications, including electronics, energy storage, and biomaterials. Combustion and Energy Conversion: Understanding the kinetics of combustion reactions is essential for optimizing the efficiency and reducing the emissions of combustion engines, power plants, and alternative energy technologies, such as fuel cells and solar cells. Biological Systems: Chemical kinetics is applied in studying enzyme kinetics, metabolic pathways, and signal transduction pathways in biological systems. This knowledge is essential for understanding cellular processes, designing pharmaceuticals, and developing therapies for diseases. © 2014 Pearson Education, Inc.  Some of the most applications Chemical Reaction Engineering: Understanding the kinetics of chemical reactions is crucial for designing and optimizing chemical processes in industries such as petrochemicals, pharmaceuticals, and materials manufacturing. Pharmaceutical Industry: Drug development often involves studying the kinetics of chemical reactions to optimize the synthesis of pharmaceutical compounds. Knowledge of reaction rates and mechanisms is essential for producing medications with the desired purity and efficiency. Environmental Science: plays a role in understanding and modeling reactions related to air and water pollution, as well as atmospheric chemistry. It helps in assessing the degradation of pollutants © 2014 Pearson Education, Inc.  Corrosion Control: Chemical kinetics is used to study the rates of corrosion reactions, allowing engineers to develop strategies to prevent or mitigate corrosion in structures and materials. Energy Storage: Kinetic studies are crucial in the development of energy storage systems, such as batteries and fuel cells. Researchers investigate reaction rates and efficiency to improve the performance of these technologies. Quality Control: Chemical kinetics can be used for quality control in various industries. By monitoring reaction rates, manufacturers can ensure consistent product quality and troubleshoot issues in real-time. © 2014 Pearson Education, Inc.  Some of the applications of chemical kinetics in pharmaceuticals Drug Development: Understanding the kinetics of chemical reactions is crucial for the synthesis and purification of active pharmaceutical ingredients (APIs). Pharmaceutical chemists study reaction rates, mechanisms, and product formation to design efficient synthetic routes for new drugs. Formulation Development: Pharmaceutical formulations, such as tablets, capsules, and injectables, involve complex chemical processes. Knowledge of kinetics is used to optimize drug release rates, stability, and bioavailability, ensuring that the drug reaches its target at the desired rate. Drug Stability: Determining the shelf life of pharmaceutical products relies on kinetic studies. Accelerated stability testing, based on chemical kinetics, helps predict how drug compounds degrade over time and under various storage conditions. This information is crucial for setting expiration dates and storage recommendations. © 2014 Pearson Education, Inc.  Enzyme Kinetics: Many pharmaceuticals act as enzyme inhibitors or substrates. Knowledge of enzyme kinetics is essential for designing drugs that effectively target specific enzymes involved in diseases, such as inhibitors for enzymes in cancer cells or HIV protease. Drug-Drug Interactions: Chemical kinetics is used to study interactions between drugs when multiple medications are taken concurrently. Drug Release Profiles: Controlled-release formulations, such as extended-release tablets and transdermal patches, rely on chemical kinetics to regulate the rate at which the drug is released into the body.. Drug Bioavailability: The kinetics of drug absorption and metabolism influence the bioavailability of a drug, which is the fraction of the administered dose that reaches the bloodstream © 2014 Pearson Education, Inc.  Key concepts and aspects of chemical kinetics Reaction Rate: The rate of a chemical reaction is the change in the concentration of reactants or products per unit of time. Reaction Mechanism: This describes the step-by-step sequence of elementary reactions that make up an overall chemical reaction. Rate Laws: Rate laws are mathematical expressions that relate the rate of a reaction to the concentrations of reactants. These laws are determined experimentally Reaction Order: The reaction order with respect to a particular reactant indicates how the concentration of that reactant affects the reaction rate. It can be zero, first, second, or even fractional. Activation Energy: This is the minimum amount of energy that reactant molecules must possess to initiate a chemical reaction. © 2014 Pearson Education, Inc.  Chemical Kinetics: The Rates of Chemical Reactions Chemical Kinetics will now provide information about the arrow! Reactants Products This gives us information on HOW a reaction occurs! © 2014 Pearson Education, Inc.  Chemical Kinetics The speed of a chemical reaction is called its reaction rate. The rate of a reaction is a measure of how fast the reaction makes products or uses reactants. The ability to control the speed of a chemical reaction is important. © 2014 Pearson Education, Inc.  Defining Rate Rate is how much a quantity changes in a given period of time. The speed you drive your car is a rate—the distance your car travels (miles) in a given period of time (1 hour). – So, the rate of your car has units of mi/hr. H +I 2 HI 2 (g) 2 (g) (g) © 2014 Pearson Education, Inc.  Defining Reaction Rate The rate of a chemical reaction is generally measured in terms of how much the concentration of a reactant decreases (or product concentration increases) in a given period of time. For reactants, a negative sign is placed in front of the definition. © 2014 Pearson Education, Inc.  We can also define the rate with respect to the product of the reaction: the rate is naturally positive. The factor of ½ in this definition is related to the stoichiometry of the reaction. © 2014 Pearson Education, Inc.  Reactant and Product Concentrations as a Function of Time © 2014 Pearson Education, Inc.  The Average Rate of the Reaction The average rate is the change in measured concentrations in any particular time period. As time goes on, the rate of a reaction generally slows down because the concentration of the reactants decreases. © 2014 Pearson Education, Inc.  Reaction Rate and Stoichiometry In most reactions, the coefficients of the balanced equation are not all the same. H2 (g) + I2 (g) 2 HI(g) For these reactions, the change in the number of molecules of one substance is a multiple of the change in the number of molecules of another. – For the above reaction, for every 1 mole of H2 used, 1 mole of I2 will also be used and 2 moles of HI made. – The concentration of HI increases at twice the rate that the concentration of H2 or I2 decreases © 2014 Pearson Education, Inc.  The Instantaneous Rate of the Reaction The instantaneous rate is the change in concentration at any one particular time. Slope at one point of a curve The instantaneous rate is determined by taking the slope of a line tangent to the curve at that particular point. First derivative of the function © 2014 Pearson Education, Inc.  H +I 2 HI 2 (g) 2 (g) (g) Using [H ], the instantaneous rate 2 at 50 s is as follows: Using [HI], the instantaneous rate at 50 s is as follows: the rate is the same whether we use one of the reactants or the product for the calculation. © 2014 Pearson Education, Inc.  where A and B are reactants, C and D are products, and a, b, c, and d are the stoichiometric coefficients. We define the rate of the reaction as follows: The change in the concentration of each substance is multiplied by 1/coefficient. © 2014 Pearson Education, Inc.  Example 13.1 Expressing Reaction Rates Consider this balanced chemical equation: In the first 10.0 seconds of the reaction, the concentration of I– dropped from 1.000 M to 0.868 M. a. Calculate the average rate of this reaction in this time interval. b. Determine the rate of change in the concentration of H+ (that is, Δ[H+]/Δt) during this time interval. Solution a. Use Equation 13.5 to calculate the average rate of the reaction. b. Use Equation 13.5 again for the relationship between the rate of the reaction and Δ[H+]/Δt. After solving for Δ[H+]/Δt , substitute the calculated rate from part (a) and calculate Δ[H+]/Δt. Chemistry: A Molecular Approach, 3rd Edition © 2014 Pearson Education, Inc. Nivaldo J. Tro Factors Affecting Reaction Rate Nature of the Reactants Temperature Catalyst Concentrations 23