Ch 6_Part 3_021812 - 2/18/2012 Equilibrium Position Factors...

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2/18/2012 1 Factors that control the position of chemical equilibria are: • Concentration • Pressure (as a result of a volume change) • Temperature NOTE: catalysts influence rate, not position of equilibrium Equilibrium Position Consider the following reaction: CoCl 4 2- (aq) + 6 H 2 O( l ) Co(H 2 O) 6 2+ (aq) + 4 Cl - (aq) HCl (aq) is added to the system at equilibrium. This increases the [Cl - ]…how will the system respond? Increase [Cl - ] results in Q>K, so reaction shifts left (blue) Changes in Concentration K c = Co(H 2 O) 6 2+ 1 M Cl 1 M 4 CoCl 4 2− 1 M
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2/18/2012 2 What if we then add AgNO 3 to precipitate Cl - ? CoCl 4 2- (aq) + 6 H 2 O( l ) Co(H 2 O) 6 2+ (aq) + 4 Cl - (aq) + Ag + (aq) AgCl (s) This decreases the [Cl - ]…how will the system respond? Decrease [Cl - ] results in Q<K, so reaction shifts right (pink) K c = Co(H 2 O) 6 2+ 1 M Cl 1 M 4 CoCl 4 2− 1 M Changes in Concentration (cont’d.) Changes in Concentration (cont’d.) Given an equilibrium equation such as : CH 4 (g) + NH 3 (g) HCN (g) + 3 H 2 (g) CH 4 (g) + NH 3 (g) HCN (g) + 3 H 2 (g) Add NH 3 Forces equilibrium to produce more product. Forces the reaction equilibrium to go back to the left and produce more of the reactants. Remove NH 3 CH 4 (g) + NH 3 (g) HCN (g) + 3 H 2 (g) Add H 2 Forces equilibrium to go toward the reactants.
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2/18/2012 3 Consider the following reaction: 2 H 2 S( g ) + O 2 ( g ) 2 S( s ) + 2 H 2 O( g ) What happens to: (a) [H 2 O] if O 2 is added? The reaction proceeds to the right so H 2 O increases. (b) [H 2 S] if O 2 is added? Some H 2 S reacts with the added O 2 to move the reaction to the right, so [H 2 S] decreases. (c) [O 2 ] if H 2 S is removed? The reaction proceeds to the left to re-form H 2 S, more O 2 is formed as well, O 2 increases. (d) [H
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This note was uploaded on 02/22/2012 for the course CHEM 142 taught by Professor Zoller,williamh during the Winter '07 term at University of Washington.

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Ch 6_Part 3_021812 - 2/18/2012 Equilibrium Position Factors...

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