CHEM 102 1nd Edition Lecture 19 Outline of Last Lecture I. Gas-phase Homogeneous EquilibriaII. Variations of KcOutline of Current Lecture I. Reaction QuotientII. Use K and Initial ConcentrationsIII. ExamplesIV. Le Chatelier’s PrincipleCurrent LectureI. Reaction Quotient- For the reaction quotient; substitute the concentrations into the expression for the reaction quotient Q and compare Q with K- For example; 2 HF H2 + F2- The reactant quotient will be Q = [H 2][F 2][HF]2- This quotient must equal k for the reaction to be in equilibriumII. Use K and Initial Concentrations- Steps: Express equilibrium concentrations of all species in terms of initial concentrations and an unknown x (ICE table) Set up the equilibrium constants using x; solve for xIII. Examples- Given: A + B C + D ; Kc = 49.0 [A] = 0.200 M [B] = 0.200 MA B C DInitial .200 0.200 0 0Changes X X -X -XEqulibrium – x 0 – x X x so you end up with x2/(0.200 – x) = 49.0 ; solve for x, x = 0.175- A + B C + D; Kc = 49.0These 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. [A] = 0.3 M [B] = 0.3 MA B C DInitial 0.300 0.300 0Change -x –x X XEquilibrium 1.3 – x 0.3 – x X x Kc = [C][D]/[A][B] = x2/(0.300 – x)2 Solve for x using the quadratic formula. IV. Le Chatelier’s Principle- A system at equilibrium will remain at equilibrium unless the system is disturbed.- Some disturbances are: Changes in concentration Changes in pressure Changes in volume Changes in temperature- When a stress is applied, the system will react in the direction away from the stress in order for the reaction to be Q =
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