Chapter 15 Overview
Chapter 15 Overview CHM 116
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This 2 page Class Notes was uploaded by Drew Notetaker on Thursday March 17, 2016. The Class Notes belongs to CHM 116 at Arizona State University taught by Cabirac in Fall 2015. Since its upload, it has received 11 views. For similar materials see General Chemistry II in Chemistry at Arizona State University.
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Date Created: 03/17/16
Chapter 15 Tuesday, February 2, 2016 2:59 PM Chemical Equilibrium o "How far to completion/ to what extent does the reaction occur?" o Important when trying to maximize production of compounds o N2 + 3H2 <--> 2NH3 How to maximize production of ammonia? By adjusting pressure and temperature o Equilibrium: a state in which there are no observable changes as time goes by Achieved when Rates of forward and reverse reactions are equal Concentrations of reactants and products remain constant When rate of forward reaction = rate of reverse reaction The reaction is at equilibrium and the concentrations of reactants and products DOES NOT CHANGE Equilibrium does not mean equal concentrations Will be established regardless of the starting concentrations of reactants and products Equilibrium constant: K_c (must be capital, sometimes just K) NO UNITS Ratio of product concentrations to reactant concentrations after an equilibrium is established Dependent on temperature When K>1 equilibrium will lie to the right and favor products K<1 will lie to left and favor reactants If Kc >10^3, products predominate over reactants, reaction is said to proceed to completion Kc range 10^-3 -- 10^3, appreciable concentrations When you flip the reaction is becomes 1/K K_p : ratio of gaseous product partial pressure(s) to gaseous reactant partial pressures after equilibrium is established Usually not equal to K_c Heterogeneous Equilibrium Reactions in which reactants and products are in different phases Concentrations of solids and pure liquids are not included in the expression for equilibrium constant ONLY FOR AQUEOUS REACTIONS o Predicting the direction of a reaction Qc: Same as Qc, but NOT AT EQUILIBRIUM Use the initial concentrations Kc>Qc : Product favored Kc=Qc : Equilibrium Kc<Qc : Reactant favored La Chatelier's Principle o 3 stresses Change concentration Does not change K Shifts reaction Change Pressure Does not change K Increase pressure, toward side with fewest moles of gas Decrease pressure, shift toward side with most moles of gas Change Reaction temp DOES change K Think of heat as reactant or product When heat is reactant, endothermic When heat is product, exothermic o Effect of a cayalst Does not shift Not change k Just gets it to equilibrium faster