CHEM 1125Q 1st Edition Lecture 18 Outline of Last Lecture Ch. 15I. Chemical Equilibrium, Reaction Quotient, Law of Mass Action, Equilibrium ExpressionsOutline of Current Lecture Ch. 15II. Gaseous EquilibriumIII. Chemical Equilibrium and Free EnergyIV. Using Q and K to Predict Reaction DirectionCurrent LectureII. Gaseous EquilibriumA. Gaseous Equilibriuma. An equilibrium expression with only gases allows us to write an alternate form of the equilibrium constant where the gas concentrations are expressed instead as partial pressures in atmi. KP = [PAa][PBb] / [PCc][PDd]b. The relationship between KC and KP is:i. KP = KC [(0.08206 L atm/mol K) x T]ΔnIII. Chemical Equilibrium and Free EnergyA. Chemical Equilibrium and Free Energya. K’s magnitude gives us the same information as the sign of ΔG0i. A reaction with K > 1 has a negative ΔG0 and is spontaneousii. A reaction with K < 1 has a positive ΔG0 and is not spontaneousb. K’s magnitude and the sign of ΔG0 allow us to solve many different problemsi. ΔG0 = -RTln(K)IV. Using Q and K to Predict Reaction DirectionA. Predicting Reaction Directiona. The direction of a reaction can be predicted by its equilibrium expression. A reaction’s equilibrium expression can also calculate its equilibrium concentration. Both of these predictions can be made by comparing QC and KCb. There are 3 possibilities when it comes to comparing QC and KCi. Q < K1. The ratio of the initial product to reactant concentration is too small2. Reactants must turn into products to reach equilibriumThese 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. The system moves in a forward directionii. Q = K1. The initial concentrations are the equilibrium concentrations so the system is already at equilibriumiii. Q > K1. The ratio of the initial product to reactant concentration is too large2. Products must turn into reactants to reach equilibrium3. The system moves in a reverse
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