Chem 113 1st Edition Lecture 19Outline of Last Lecture I. The reaction Quotient QII. Ways of expressing Q and calculating KIII. Determining the direction of a reactionOutline of Current Lecture IV. Equilibrium trending towards equal ratesV. Le Châtelier’s PrincipleVI. The Effect of a change in concentrationVII. The Effect of a change in Pressure (Volume)Current LectureI. Equilibrium trending towards equal ratesa. If the concentration of a reactant is increase, the Kc and Q are decreasedII. Le Châtelier’s Principlea. When a chemical system at equilibrium is disturbed, it reattains equilibrium by undergoing a net reaction that reduces the effect of the disturbanceb. A system is disturbed when a change in conditions forces it temporarily out of equilibriumc. The system responds to a disturbance by a shift in the equilibrium positiond. A shift to the left is a net reaction from product to reactante. A shift to the right is a net reaction from reactant to productIII. The Effect of a change in concentrationa. If the concentration of a reactant/product increases, the system reacts to consume some of iti. If a reactant is added, the equilibrium position shifts to the rightii. If a product is added, the equilibrium position shifts to the leftThese 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.b. If the concentration of a reactant/product decreases, the system reacts to regenerate some of iti. If a reactant is removed, the equilibrium position shifts to the leftii. If a product is removed, the equilibrium position shifts to the rightc. Only substances that appear in the expression for Q can have an effectd. A change in concentration has no effect on the value of KIV. The Effect of a change in Pressure (Volume)a. Changes in pressure affect equilibrium systems containing gaseous componentsi. Changing the concentration of a gaseous component causes the equilibrium to shift accordinglyii. Adding an inert gas has no effect on the equilibrium position, as long as the volume does not change1. This is because all concentrations and partial pressures remain unchangediii. Changing the volume of the reaction vessel will cause equilibrium to shift if Δngas≠0V. The Effect of a change in temperaturea. To determine the effect of a change in temperature on equilibrium, heat is considered a component of the systemb. Heat is a product in an exothermic reaction (ΔHrxn<0)c. Heat is a reactant in an endothermic reaction (ΔHrxn>0)d. An increase in temperature adds heat, which favors the endothermic reactione. A decrease in temperature removes heat, which favors the exothermic
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