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The Reading is for the next class. Problems are for that day’s class. Problems for each week (MWF) are due the following Monday.
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Reaction quotient PCPDPCPD PAPBPAPB ab c d Q = or [C] c [D] d [A] a [B] b
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Reaction quotient PCPDPCPD PAPBPAPB ab c d Q = P A, P B, etc. not at equilibrium
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Reaction quotient PCPDPCPD PAPBPAPB ab c d Q = Q will go to the value of K as the partial pressures go to equilibrium
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Q vs K can predict where the reaction is in respect to equilibrium.
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PCPDPCPD PAPBPAPB ab c d K = PCPDPCPD PAPBPAPB ab c d Q = Q < K aA + bB cC + dD
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PCPDPCPD PAPBPAPB ab c d K = PCPDPCPD PAPBPAPB ab c d Q = Q < K aA + bB cC + dD Too much reactant, not enough product.
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PCPDPCPD PAPBPAPB ab c d K = PCPDPCPD PAPBPAPB ab c d Q = Q < K Q > K aA + bB cC + dD
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PCPDPCPD PAPBPAPB ab c d K = PCPDPCPD PAPBPAPB ab c d Q = Q < K Q > K aA + bB cC + dD Too much product, not enough reactant.
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PCPDPCPD PAPBPAPB ab c d K = Q = Q > K aA + bB cC + dD Q < K Large vs c d PCPDPCPD c d PCPDPCPD ab PAPBPAPB ab PAPBPAPB
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Q = c d PCPDPCPD ab PAPBPAPB
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Exercise page 291 P 4 2 P 2 K = 1.39 @ 400 o C 1.40 mol P 4 1.25 mol P 2 Volume = 25.0 L
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P 4 2 P 2 Q = (P P ) 2 2 P 4
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P 4 2 P 2 Q = (P P ) 2 2 P 4 P = nRT V T = 673 K V = 25.0 L R = 0.0820578 L atm mol -1 K -1
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P 4 2 P 2 Q = (P P ) 2 2 P 4 P P = nRT V 4 = (1.4)(0.0820578)(673) 25.0 = 3.09 atm
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P 4 2 P 2 Q = (P P ) 2 2 P 4 P P = nRT V 2 = (1.25)(0.0820578)(673) 25.0 = 2.76 atm P P = nRT V 4 = (1.4)(0.0820578)(673) 25.0 = 3.09 atm
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P 4 2 P 2 Q = (P P ) 2 2 P 4 P P = 2 2.76 atm P P = 4 3.09 atm = (2.76) 2 3.09 =
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P 4 2 P 2 (P P ) 2 2 P 4 P P = 2 2.76 atm P P = 4 3.09 atm = (2.76) 2 3.09 = 2.46 Q = K = 1.39
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P 4 2 P 2 (P P ) 2 2 P 4 P P = 2 2.76 atm P P = 4 3.09 atm = (2.76) 2 3.09 = 2.46 Q = K = 1.39 P 4 2 P 2
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Converting between partial pressures and concentrations.
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Converting between partial pressures and concentrations. Concentration = moles V
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Converting between partial pressures and concentrations. Concentration = moles V PV = nRT
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Converting between partial pressures and concentrations. Concentration = moles V For gas ‘A’[A] = nAnA V PV = nRT
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Converting between partial pressures and concentrations. Concentration = moles V For gas ‘A’[A] = nAnA V = PAPA RT PV = nRT
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Converting between partial pressures and concentrations. Concentration = moles V For gas ‘A’[A] = nAnA V = PAPA RT P A = RT[A] PV = nRT
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P A = RT[A] 2 NO 2(g) N 2 O 4(g)
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P A = RT[A] 2 NO 2(g) N 2 O 4(g) P ref = 1 atm
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P A = RT[A] 2 NO 2(g) N 2 O 4(g) P ref = 1 atm P N O 24 /P ref (P NO 2 /P ref ) 2 = K
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P A = RT[A] 2 NO 2(g) N 2 O 4(g) P ref = 1 atm 4 /P ref (P NO 2 /P ref ) 2 = K P N O 2 2 4 = RT[N 2 O 4 ]
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P A = RT[A] 2 NO 2(g) N 2 O 4(g) P ref = 1 atm 4 /P ref (P NO 2 /P ref ) 2 = K P N O 2 2 4 = RT[N 2 O 4 ] P NO 2 = RT[NO 2 ]
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2 NO 2(g) N 2 O 4(g) 4 /P ref (P NO 2 /P ref ) 2 = K P N O 2 2 4 = RT[N 2 O 4 ] P NO 2 = RT[NO 2 ] [N 2 O 4 ](RT/P ref ) [NO 2 ] 2 (RT/P ref ) = [N 2 O 4 ] [NO 2 ] 2 x RT P ref ) ( K =
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2 NO 2(g) N 2 O 4(g) [N 2 O 4 ](RT/P ref ) [NO 2 ] 2 (RT/P ref ) = x K = [N 2 O 4 ] [NO 2 ] 2 [N 2 O 4 ] [NO 2 ] 2 = K RT P ref ) ( RT P ref ) (
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[N 2 O 4 ] [NO 2 ] 2 = K RT P ref ) ( aA + bB cC + dD c = K [C] c [D] d PCPDPCPD PAPBPAPB ab d [A] a [B] b = K ( RT P ref ) a+b-c-d ?
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[C] c [D] d [A] a [B] b = K ( RT P ref ) a+b-c-d Exercise page 297 CH 4 + H 2 O CO + 3 H 2 K = 0.172 [H 2 ]=[CO]=[H 2 O]= 0.00642 mol L -1
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[C] c [D] d [A] a [B] b = K ( RT P ref ) a+b-c-d CH 4 + H 2 O CO + 3 H 2 K = 0.172 [H 2 ]=[CO]=[H 2 O]= 0.00642 mol L -1 (0.00642) 4 [CH 4 ](0.00642) = 0.172 ( RT P ref ) -2
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[CH 4 ] = 0.172 ( RT P ref ) -2 CH 4 + H 2 O CO + 3 H 2 [CH 4 ] = K(RT) -2 = 3.153 x 10 -5 (0.00642) 3 3.153 x 10 -5 = 8.39 x 10 -2 mol L -1
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Le Chatelier’s Principle
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A system in equilibrium that is subjected to a stress reacts in a way that counteracts the stress.
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Le Chatelier’s Principle Any system in chemical equilibrium, as a result of the variation in one of the factors determining the equilibrium, undergoes a change such that, if this change had occurred by itself, it would have introduced a variation of the factor considered in the opposite direction.
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Le Chatelier’s Principle Any system in chemical equilibrium, as a result of the variation in one of the factors determining the equilibrium, undergoes a change such that, if this change had occurred by itself, it would have introduced a variation of the factor considered in the opposite direction.
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Le Chatelier’s Principle A system in equilibrium that is subjected to a stress reacts in a way that counteracts the stress. Stress = a factor affecting equilibrium
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K = [C] c [D] d [A] a [B] b Anything causing a change in the concentration (or partial pressure) of a reactant or product is a stress.
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Factors affecting equilibrium:
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temperature
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Factors affecting equilibrium: temperature pressure
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Factors affecting equilibrium: temperature pressure volume
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Factors affecting equilibrium: temperature pressure removal or addition of product volume
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Factors affecting equilibrium: temperature pressure removal or addition of reactant volume removal or addition of product
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Removal or addition of a reactant or product.
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Removal or addition of a reactant or product. Increases or decreases concentration.
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PAPA [A] PBPB [B] Removal or addition of a reactant or product. Increases or decreases concentration.
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K = [B] [A]
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I 2 + H 2 2 HI
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P HI = 3.009 atm PIPI 2 = 0.4756 atm PHPH 2 = 0.2056 atm
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I 2 + H 2 2 HI = 0.4756 atm = 0.2056 atm = 3.009 atm P HI ()2)2 PIPI 2 PIPI 2 ()PHPH 2 PHPH 2 () = K
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I 2 + H 2 2 HI = 0.4756 atm = 0.2056 atm = 3.009 atm P HI ()2)2 PIPI 2 PIPI 2 ()PHPH 2 PHPH 2 () = K (3.009) 2 (0.4756)(0.2056) =
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I 2 + H 2 2 HI = 0.4756 atm = 0.2056 atm = 3.009 atm P HI ()2)2 PIPI 2 PIPI 2 ()PHPH 2 PHPH 2 () = K (3.009) 2 (0.4756)(0.2056) = 92.60
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I 2 + H 2 2 HI Increase P I 2 to 2.00 atm.
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I 2 + H 2 2 HI K = 92.60 Start P 2.000 0.2056 3.009 PP 2 nd eq P Increase P I 2 to 2.000 atm
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I 2 + H 2 2 HI K = 92.60 Start P 2.000 0.2056 3.009 PP 2 nd eq P Increase P I 2 to 2.000 atm -x -x +2x
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I 2 + H 2 2 HI K = 92.60 Start P 2.000 0.2056 3.009 PP 2 nd eq P Increase P I 2 to 2.000 atm -x -x +2x 2.000-x 0.2056-x 3.009+2x
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I 2 + H 2 2 HI K = 92.60 Start P 2.000 0.2056 3.009 PP 2 nd eq P Increase P I 2 to 2.000 atm -x -x +2x 2.000-x 0.2056-x 3.009+2x 92.6 = (3.009+2x) 2 (2.000-x)(0.2056-x) =
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92.6 = (3.009+2x) 2 (2.000-x)(0.2056-x) =
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92.6 = (3.009+2x) 2 (2.000-x)(0.2056-x) = (9.054 + 12.036x + 4x 2 ) (0.4112 - 2.2056x + x 2 ) = 92.6
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92.6 = (3.009+2x) 2 (2.000-x)(0.2056-x) = (9.054 + 12.036x + 4x 2 ) = 92.6 9.054 + 12.036x + 4x 2 = 92.6(0.4112 - 2.2056x + x 2 ) (0.4112 - 2.2056x + x 2 )
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92.6 = (3.009+2x) 2 (2.000-x)(0.2056-x) = (9.054 + 12.036x + 4x 2 ) = 92.6 (0.4112 - 2.2056x + x 2 ) (0.4112 - 2.2056x + x 2 ) 9.054 + 12.036x + 4x 2 = 38.08 - 204.24x + 92.6x 2 9.054 + 12.036x + 4x 2 = 92.6
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9.054 + 12.036x + 4x 2 = 38.08 - 204.24x + 92.6x 2 88.60x 2 - 216.276x + 29.023 = 0 x = -b b 2 - 4 ac 2a abc =
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9.054 + 12.036x + 4x 2 = 38.08 - 204.24x + 92.6x 2 88.60x 2 - 216.276x + 29.023 = 0 x = -b b 2 - 4 ac 2a abc = 0.142 or 2.30
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Start P 2.000 0.2056 3.009 PP 2 nd eq P -x -x +2x 2.000-x 0.2056-x 3.009+2x 0.142 or 2.30x = I 2 + H 2 2 HI
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Start P 2.000 0.2056 3.009 PP 2 nd eq P -x -x +2x 2.000-x 0.2056-x 3.009+2x 0.142 or 2.30x = I 2 + H 2 2 HI x = 2.30 would give a negative pressure for I 2
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Start P 2.000 0.2056 3.009 PP 2 nd eq P -0.142 -0.142 0.284 1.858 0.0636 3.293 0.142 or 2.30x = I 2 + H 2 2 HI
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Calculate K with new partial pressures.
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Calculate K with new partial pressures. (3.293) 2 (1.858)(0.0636) =
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Calculate K with new partial pressures. (3.293) 2 (1.858)(0.0636) = 91.77 K given = 92.60
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Changing volume of system
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V 1 P
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Changing volume of system V 1 P If V is reduced, P increases. PV = nRT
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Changing volume of system V 1 P If V is reduced, P increases. Le Chatlier’s principle requires that the equilibrium shift so that P decreases.
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2 NO 2(g) N 2 O 4(g)
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2 NO 2(g) N 2 O 4(g) An increase in pressure should favor an increase in the product, N 2 O 4.
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2 NO 2(g) N 2 O 4(g) An increase in pressure should favor an increase in the product, N 2 O 4. Each N 2 O 4 produced means a loss of two NO 2 molecules, a net loss of one molecule and a lower pressure.
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2 NO 2(g) N 2 O 4(g) A decrease in pressure favors a shift to NO 2.
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Raising or lowering the temperature
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Some reactions liberate heat to form products.
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Raising or lowering the temperature Some reactions liberate heat to form products. This is an exothermic reaction.
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Raising or lowering the temperature This is an endothermic reaction. Other reactions absorb heat to produce products.
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Raising the temperature of an endothermic reaction will favor the formation of more product. R P
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Raising the temperature of an exothermic reaction will favor the formation of more reactant. R P
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NaOH (s) + H 2 O (l) Na + (aq) + OH - (aq) + H 2 O (l)
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The solution of solid sodium hydroxide into water is exothermic.
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K = [P] [R]
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K = [P] [R] If a reaction is exothermic and the temperature is raised, K will decrease.
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K = [P] [R] If a reaction is endothermic and the temperature is raised, K will increase.
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Driving reactions to completion
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Completion = 100% yield of product
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Cl - (aq) + Ag + (aq) AgCl (s)
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AgCl precipitates from the solution.
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Cl - (aq) + Ag + (aq) AgCl (s) AgCl precipitates from the solution. As the AgCl precipitates, product is removed from solution.
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Cl - (aq) + Ag + (aq) AgCl (s)
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N 2 + 3 H 2 2 NH 3 All gases
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N 2 + 3 H 2 2 NH 3 All gases exothermic
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N 2 + 3 H 2 2 NH 3 All gases exothermic cool
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N 2 + 3 H 2 2 NH 3 All gases exothermic cool
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N 2 + 3 H 2 2 NH 3 Although a lower temperature favors more NH 3 formed, the lower temperature also leads to a very slow reaction.
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N 2 + 3 H 2 2 NH 3 An increase in pressure should favor product.
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N 2 + 3 H 2 2 NH 3 An increase in pressure should favor product.
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N 2 + 3 H 2 2 NH 3 Ultimate solution: react at high Temperature to speed up reaction, cool until NH 3 becomes liquid. Remove from reaction vessel and repeat.
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(time) CONCENTRATIONCONCENTRATION
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Heterogeneous equilibrium
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Involves at least two phases.
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Heterogeneous equilibrium Involves at least two phases. What is the concentration of a pure liquid or a pure solid?
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Concentrations are not a valid way to define a pure liquid or solid.
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Concentrations are not a valid way to define a pure liquid or solid. Moles water Liters solvent =?
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The concentration of a pure liquid or solid is defined as 1.
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Law of Mass Action
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1. Gases enter equilibrium expressions as partial pressures in atmospheres.
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Law of Mass Action 1. Gases enter equilibrium expressions as partial pressures in atmospheres. 2. Dissolved species enter as concentrations in mol L -1.
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Law of Mass Action 1. Gases enter equilibrium expressions as partial pressures in atmospheres. 2. Dissolved species enter as concentrations in mol L -1. 3. Pure solids and liquids are represented by 1 at equilibrium, a dilute solvent is 1.
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Law of Mass Action 1. Gases enter equilibrium expressions as partial pressures in atmospheres. 2. Dissolved species enter as concentrations in mol L -1. 3. Pure solids and liquids are represented by 1 at equilibrium, a dilute solvent is 1. 4. Partial pressures or concentrations of products appear in the numerator, reactants in the denominator. Each is raised to the power of its coefficient.
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hemoglobin
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Fe
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heme Fe
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Fe heme + O 2 Fe heme O 2
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4 heme Fe sites to bond O 2
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Increase P O more Fe heme O 2 Fe heme + O 2 Fe heme O 2 2
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4 heme Fe sites to bond O 2 Fe heme O 2 Fe heme + O 2 Fe heme O 2 Increase P O by changing local atmosphere. 2 Increase P O more 2
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4 heme Fe sites to bond O 2 Decrease P O less Fe heme O 2 Fe heme + O 2 Fe heme O 2 2
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4 heme Fe sites to bond O 2 Decrease P O less Fe heme O 2 Fe heme + O 2 Fe heme O 2 2 Decrease P O 2 by going to higher altitude.
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Fe heme + CO Fe heme CO Fe heme + O 2 Fe heme O 2
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Fe heme + CO Fe heme CO Fe heme + O 2 Fe heme O 2 POPO 2 = 0.20 atm Affinity for CO over O 2 factor of 200+.
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Fe heme + CO Fe heme CO Fe heme + O 2 Fe heme O 2 POPO 2 = 0.20 atm Affinity for CO over O 2 factor of 200+. CO 1 x 10 3 ppm < 1% P CO < 0.01 atm
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Fe heme + CO Fe heme CO Fe heme + O 2 Fe heme O 2 POPO 2 = 0.20 atm CO 1 x 10 3 ppm < 1% P CO < 0.01 atm K heme-CO >> K heme-O 2
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