Chem 113 1st Edition Lecture 7Outline of Last Lecture I. Patterns of Spontaneous and Nonspontaneous reactionsII. Effects of temperature of reaction spontaneityIII. Coupled Reactions: Using ΔGrxn to drive nonspontaneous reactionsOutline of Current LectureIV. Coupling Reactions (continued)V. Chemical KineticsCurrent LectureI. Coupling Reactionsa. Overall, this process is spontaneous (ΔG<0)II. Chemical Kineticsa. A balanced chemical reaction predicts what can happen, but not what does happeni. Descriptions of reactions1. Speed of a reaction2. How far the reaction will proceed3. Absorption or release of energy4. How the reaction occursb. Reaction rates varyi. Examples:1. An explosion (combustion)2. Ripening over time3. Rusting4. Agingii. Factors that affect reaction rates1. Concentration: frequency of molecular collisions2. Physical state (phase): molecules must mixThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.3. Temperature: effects the energy of molecular collisions and the frequency of molecular collisions4. Catalyst: rate-accelerating agentiii. Reaction rates measure how quickly a reactant is converted into a product, it tells how long a reaction to take until it reaches completion1. Change in concentration/change in time (in mol/L*s)c. Molecular collisionsi. Energetic collisions during reactions form productsii. Bimolecular process1. A+B products2. A and B must collide in the right orientation for the reaction to occurd. Expressing the reaction ratei. Reaction rate is measured in terms of the changes in concentrations of reactants or products per unit timeii. For the general reaction A B we measure the concentration of A at t1 and at t21.Rate=−change∈concentrationof Achange∈time=−ConcA 2−ConcA 1t 2−t 1a. Square brackets indicate a concentration in mole per literb. The negative sign is used because the concentration of A is decreasing, giving the rate a positive valueiii. Three ways to describe the rate1. Average ratea. Amount the observable changes over a particular intervalb. Usually varies depending on the time considered2. Instantaneous ratea. Rate at an specific timeb. Slope of the line tangent to the curve (take the derivative)3. Initial ratea. Rate at the very beginning of the reactionb. Will depend on how fast we can measure the beginning of the
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