16_Chapt15_09

# 16_Chapt15_09 - Gas Phase Equilibrium Chemical Equilibrium...

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Mary J. Bojan Chem 110 1 Gas Phase Equilibrium Chemical Equilibrium Equilibrium Constant K eq Equilibrium constant expression Relationship between K p and K c Heterogeneous Equilibria Meaning of K eq Calculations of K c Solving Equilibrium Problems USING AN EQUILIBRIUM CONSTANT Information obtained from K c 1. Predict direction of a reaction Q reaction quotien 2. Obtaining equilibrium concentrations of reactants and products.

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Mary J. Bojan Chem 110 2 Equilibrium Equilibrium is achieved when opposing processes proceed at equal rates. equilibria previously discussed Eg.
Mary J. Bojan Chem 110 3 Chemical Equilibrium In chemical equilibria, forward and reverse reactions occur at equal rates. N 2 O 4 (g) 2NO 2 (g) colorless brown

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Mary J. Bojan Chem 110 4 Achieving equilibrium Initial State : reactants only Initial state : products only
Mary J. Bojan Chem 110 5 Equilibrium Constant Equilibrium point of any reaction is characterized by a single number . Example: 2NO 2A N 2 O 4 B In general: jA + kB pR + qS

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Mary J. Bojan Chem 110 6 EXPRESSION for K eq What is the equilibrium constant expression for the Haber process? N 2 (g) + 3H 2 (g) 2NH 3 (g)
Mary J. Bojan Chem 110 7 Equilibrium Constant The ratio of equilibrium concentrations will be constant: K eq is the equilibrium constant for the reaction. It is a NUMBER . K eq (the number) DOES NOT depend on concentration It’s a function of temperature only. Notation: K eq = K c concentration […] is expressed in M (mol/L) concentration is expressed using partial pressures in atm K eq = K p

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Mary J. Bojan Chem 110 8 When given K eq how do I know if it is K c or K p ? Use context of problem. If concentrations are given in M , then K eq = K c If concentrations are given in P , then K eq = K p where Δ n = n prod n react Relationship between K p and K c
Mary J. Bojan Chem 110 9 Calculating K p and K c Equilibrium concentrations of NH 3 , N 2 , and H 2 were determined at 472 ° C. [H 2 ] = 0.1207M [N 2 ] = 0.0402M [NH 3 ] = 0.00272M Find K c and K p . 2NH 3 (g) N 2 (g) + 3H 2 (g)

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Chem 110 10 Heterogeneous Equilibria involves reactants and products in more than one phase 3Fe(s) + 4H 2 O(g) Fe 3 O 4 (s)+4H 2 (g) K eq = Fe 3 O 4 [ ] H 2 [ ] 4 Fe [ ] 3 H 2 O [ ] 4 What is [Fe]? [Fe 3 O 4 ]? Activities of pure solids and liquids = 1.
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## This note was uploaded on 07/16/2011 for the course CHEM 110 taught by Professor Hofmann,brucerob during the Spring '08 term at Penn State.

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16_Chapt15_09 - Gas Phase Equilibrium Chemical Equilibrium...

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