Bài giảng hóa bằng tiếng anh Chemical Equilibrium

Chemical Equilibrium Hemoglobin • protein (Hb) found in red blood cells that reacts with O2 enhances the amount of O2 that can be carried through the blood stream Hb + O2  HbO2 the Hb represents the entire protein – it is not a chemical formula the  represents that the reaction is in dynamic equilibrium Hemoglobin Equilibrium System Hb + O2  HbO2 • the concentrations of Hb, O2, and HbO2 are all • interdependent the relative amounts of Hb, O2, and HbO2 at equilibrium are related to a constant called the equilibrium constant, K  the larger the value of K, the more product is found at equilibrium • changing the concentration of any one of these necessitates changing the other concentrations to reestablish equilibrium O2 Transport in the lungs, with high concentration of O2, the equilibrium shifts to combine the Hb and O2 together to make more HbO2 in the cells, with low concentration of O2, the equilibrium shifts to break down the HbO2 and increase the amount of free O2 Hb + O O22 O  in in2 lungs cells HbO2 Fetal Hemoglobin, HbF HbF + O2  HbFO2 • fetal hemoglobin’s • equilibrium constant is larger than adult hemoglobin because fetal hemoglobin is more efficient at binding O2, O2 is transferred to the fetal hemoglobin from the mother’s hemoglobin in the placenta Hb + O2 HbO  HbO 22 O2 HbF Hb + O2 HbFO22  HbFO Oxygen Exchange between Mother and Fetus Reaction Dynamics • when a reaction starts, the reactants are consumed and products are made  forward reaction = reactants  products  therefore the reactant concentrations decrease and the product concentrations increase  as reactant concentration decreases, the forward reaction rate decreases • eventually, the products can react to reform some of the reactants  reverse reaction = products  reactants  assuming the products are not allowed to escape  as product concentration increases, the reverse reaction rate increases • processes that proceed in both the forward and reverse direction are said to be reversible  reactants  products Time [Red] Hypothetical Reaction Red  Blue [Blue] 0.400 0.000 10 0.208 0.096 20 0.190 0.105 30 0.180 0.110 40 0.174 0.113 50 0.170 0.115 60 0.168 0.116 70 0.167 0.117 80 0.166 0.117 90 0.165 0.118 100 0.165 0.118 110 0.164 0.118 120 0.164 0.118 130 0.164 0.118 140 0.164 0.118 150 0.164 0.118 The reaction slows over time, But the Red molecules never run out! At some time between 100 and 110 sec, the concentrations of both the Red and the Blue molecules no longer change – equilibrium has been established Notice that equilibrium does not mean that the concentrations are equal! Once equilibrium is established, the rate of Red molecules turning into Blue is the same as the rate of Blue molecules turning into Red Hypothetical Reaction Red  Blue [Red] [Blue] Concentration vs Time for Red > Blue 0.45 Concentration 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 20 40 60 80 Time, sec 100 120 140 Rate Reaction Dynamics Rate Forward Rate Reverse Time 10 Dynamic Equilibrium • as the forward reaction slows and the reverse • • reaction accelerates, eventually they reach the same rate dynamic equilibrium is the condition where the rates of the forward and reverse reactions are equal once the reaction reaches equilibrium, the concentrations of all the chemicals remain constant because the chemicals are being consumed and made at the same rate 11 H2(g) + I2(g)  HI(g) at time 0, there are only reactants in the mixture, so only the forward reaction can take place [H2] = 8, [I2] = 8, [HI] = at time 16, there are both reactants and products in the mixture, so both the forward reaction and reverse reaction can take place [H2] = 6, [I2] = 6, [HI] = 12 H2(g) + I2(g)  HI(g) at time 32, there are now more products than reactants in the mixture − the forward reaction has slowed down as the reactants run out, and the reverse reaction accelerated [H2] = 4, [I2] = 4, [HI] = at time 48, the amounts of products and reactants in the mixture haven’t changed – the forward and reverse reactions are proceeding at the same rate – it has reached equilibrium 13 H2(g) + I2(g)  HI(g) Concentration  As the reaction proceeds, the [H2] and [I2] decrease and the [HI] increases And since the product concentration is increasing, the reverse reaction rate speeds up Since the [HI] at equilibrium is larger than the [H2] or [I2], we say the position of equilibrium favors products Once equilibrium is established, the concentrations no longer change Time  Equilibrium Established 14 Equilibrium  Equal • the rates of the forward and reverse reactions are • • • equal at equilibrium but that does not mean the concentrations of reactants and products are equal some reactions reach equilibrium only after almost all the reactant molecules are consumed – we say the position of equilibrium favors the products other reactions reach equilibrium when only a small percentage of the reactant molecules are consumed – we say the position of equilibrium favors the reactants 15 An Analogy: Population Changes When Country A citizens feel overcrowded, some will emigrate to Country B 16 An Analogy: Population Changes However, as time passes, emigration will occur in both directions at the same rate, leading to populations in Country A and Country B that are constant, though not necessarily equal 17 [...]... change Time  Equilibrium Established 14 Equilibrium  Equal • the rates of the forward and reverse reactions are • • • equal at equilibrium but that does not mean the concentrations of reactants and products are equal some reactions reach equilibrium only after almost all the reactant molecules are consumed – we say the position of equilibrium favors the products other reactions reach equilibrium when...Dynamic Equilibrium • as the forward reaction slows and the reverse • • reaction accelerates, eventually they reach the same rate dynamic equilibrium is the condition where the rates of the forward and reverse reactions are equal once the reaction reaches equilibrium, the concentrations of all the chemicals remain constant because the chemicals are being consumed and made... at the same rate – it has reached equilibrium 13 H2(g) + I2(g)  2 HI(g) Concentration  As the reaction proceeds, the [H2] and [I2] decrease and the [HI] increases And since the product concentration is increasing, the reverse reaction rate speeds up Since the [HI] at equilibrium is larger than the [H2] or [I2], we say the position of equilibrium favors products Once equilibrium is established, the... molecules are consumed – we say the position of equilibrium favors the products other reactions reach equilibrium when only a small percentage of the reactant molecules are consumed – we say the position of equilibrium favors the reactants 15 An Analogy: Population Changes When Country A citizens feel overcrowded, some will emigrate to Country B 16 An Analogy: Population Changes However, as time passes, emigration