5 - 1Chemistry for Allied Health: Equilibrium CHAPTER 9 Chemical Equilibrium Rates of Reaction Equilibrium

5 - 2Chemistry for Allied Health: Equilibrium Energy Rxn Progress 2H 2(g) + O 2(g)  2H 2 O + Energy Just because something has the potential to react doesn’t mean it will do so immediately. doesn’t mean it will do so immediately. Just because something has the potential to react doesn’t mean it will do so immediately. doesn’t mean it will do so immediately. H 2(g) O 2(g) may stay together for lifetime without reacting to form water. H 2(g) + O 2(g) may stay together for lifetime without reacting to form water. Reaction Rates Very stable product (  H < 0)  H

5 - 3Chemistry for Allied Health: Equilibrium Chemical kinetics The study of reaction rates (speed) Enthalpywill &not Entropy EnthalpyOnly tell us if a reaction will &occur but not how long it will Entropytake. Kineticstime required KineticsMeasures the time required for a reaction to occur.

5 - 4Chemistry for Allied Health: Equilibrium Chemical kinetics Kinetics of a chemical reaction can tell us - how long how long it will take for a reaction to reach completion. (mechanism how chemicals react to form products (mechanism). catalysts effects of catalysts and enzymes. how to control how to control a reaction.

5 - 5Chemistry for Allied Health: Equilibrium Speed at which reactant is used up. Speed at which product forms. burning Oxidation: Paper burning Paper turning yellow rusting Oxidation: Nails rusting Reaction Rates Fast: Slow:

5 - 6Chemistry for Allied Health: Equilibrium Figure 9.1 Reaction Rates Fast: Slow: Slower:

5 - 7Chemistry for Allied Health: Equilibrium A reaction won’t happen if: Effective collisions aligned Molecules are not aligned correctly. energy to break bonds Insufficient energy to break bonds. N 2 O 2

5 - 8Chemistry for Allied Health: Equilibrium 3. They have to have enough E. For reactants to make products: collide 1. Molecules must collide (solvents really help) aligned 2. They have to be aligned correctly. (Parked cars don’t collide) Effective collisions

5 - 9Chemistry for Allied Health: Equilibrium Activation Energy activation energy The activation energy E act Is the minimum energy needed for a reaction to take place upon proper collision of reactants.

5 - 10Chemistry for Allied Health: Equilibrium Show the  E during a reaction. Show the  E during a reaction. Energy diagrams  H E act Activation energy E act Energy A temporary state where bonds are reforming. Activated Complex Activated Complex

5 - 11Chemistry for Allied Health: Equilibrium Factors Influencing Rxn Rates Reaction rates can be affected by : polar vs. nonpolar 1. Reactant structure( polar vs. nonpolar ) physical state of reactants vapor vs liq ( vapor vs liq. ) 2. Concentration 2. Concentration of reactants medications ( medications ) surface area sugar cube vs crystals surface area ( sugar cube vs crystals ) 3. Temperature hypothermia & metabolism ( hypothermia & metabolism ) 4. Catalyst H 2 O 2 & blood 4. Catalyst ( H 2 O 2 & blood )

5 - 12Chemistry for Allied Health: Equilibrium If reactant concentration Increase reactant concentrationthen # of collisions Increase # of collisionsso reaction rate Increase reaction rate. Reaction Rates Concentration : 1.More Reactants: More cars  More collisions

5 - 13Chemistry for Allied Health: Equilibrium Reaction Rates Concentration: 1.More Reactants: 8 blocks: 34 surfaces 8 blocks: 24 surfaces More surface area  More collisions

5 - 14Chemistry for Allied Health: Equilibrium Reaction Rates Temperature: 2.Higher Temperature: Faster cars  More collisions More Energy  More collisions Reacting molecules move faster, providing colliding molecules w/ E act.

5 - 15Chemistry for Allied Health: Equilibrium Reaction Rates Catalyst: 3.Adding a Catalyst: Lower E act  More collisions Uncatalysed reaction

5 - 16Chemistry for Allied Health: Equilibrium Reaction Rates Catalyst: 3.Adding a Catalyst: Lower E act  More collisions Uncatalysed reaction Catalysed reaction Lower activation energy Alters reaction mechanism but not products Is not used up during the reaction.

5 - 17Chemistry for Allied Health: Equilibrium Reaction Rates Catalyst: 3.Adding a Catalyst: Lower E act  More collisions Uncatalysed reaction Catalysed reaction Lower activation energy Enzymes Enzymes are biological catalysts.

5 - 18Chemistry for Allied Health: Equilibrium Catalytic Converter

5 - 19Chemistry for Allied Health: Equilibrium Catalytic Converter

5 - 20Chemistry for Allied Health: Equilibrium Learning Check State the effect of each on the rate of reaction as (I) increases, (D) decreases, or (N) no change. A. Increasing the temperature. B. Removing some of the reactants. C. Adding a catalyst. D. Placing the reaction flask in ice. E. Increasing the concentration of a reactant.

5 - 21Chemistry for Allied Health: Equilibrium Solution State the effect of each on the rate of reaction as (I) increases, (D) decreases, or (N) no change. A. Increasing the temperature.(I) B. Removing some of the reactants. (D) C. Adding a catalyst. (I) D. Placing the reaction flask in ice. (D) E. Increasing the concentration of a reactant. (I)

5 - 22Chemistry for Allied Health: Equilibrium Learning Check Indicate the effect of each factor listed on the rate of the following reaction as (I) increases, (D) decreases, or (N) none: 2CO(g) + O 2 (g)  2CO 2 (g) A. Raising the temperature B. Removing O 2 C. Adding a catalyst D. Lowering the temperature

5 - 23Chemistry for Allied Health: Equilibrium Solution Indicate the effect of each factor listed on the rate of the following reaction as (I) increases, (D) decreases, or (N) none: 2CO(g) + O 2 (g)  2CO 2 (g) A. Raising the temperature (I) B. Adding O 2 (D) C. Adding a catalyst (I) D. Lowering the temperature (D)

5 - 24Chemistry for Allied Health: Equilibrium Equilibrium A state where the forward and reverse conditions occur at the same rate. Dynamic Equilibrium I’m in static equilibrium.

5 - 25Chemistry for Allied Health: Equilibrium Chemical equilibrium Dynamic process Rate of forward Rxn = Rate of reverse Rxn H 2 O (l) H 2 O (g) H 2 O (l) H 2 O (g) (reactant) (product) (reactant) (product) Dynamic Equilibrium Concentration of reactants and products remain constant over time.

5 - 26Chemistry for Allied Health: Equilibrium Equilibrium and reaction rates A point is ultimately reached where the rates of the forward and reverse reactions are the same. At this point, equilibrium is achieved. Reaction rate Time H 2 O (l) H 2 O (g) H 2 O (l) H 2 O (g) (reactant) (product)

5 - 27Chemistry for Allied Health: Equilibrium Figure 9.8 2SO 2(g) + O 2(g) 2SO 3(g) At Equilibium SO 2(g) +O 2(g) Initially SO 3(g) Initially

5 - 28Chemistry for Allied Health: Equilibrium Figure 9.9 2SO 2(g) + O 2(g) 2SO 3(g) At Equilibium SO 2(g) +O 2(g) Initially SO 3(g) Initially

5 - 29Chemistry for Allied Health: Equilibrium Figure 9.10 N 2(g) + O 2(g) 2NO (g) At Equilibium N 2(g) +O 2(g) Initially NO (g) Initially

5 - 30Chemistry for Allied Health: Equilibrium Equilibrium Concentration Time KineticEquilibrium Region Concentration of reactants and products remain constant over time.

5 - 31Chemistry for Allied Health: Equilibrium [C]c [D]d[A]a [B]b[C]c [D]d[A]a [B]b K eq = Equilibrium constant (K) Equilibrium expression (for any reaction at constant temperature) aA + bB cC + dD moles per liter coefficients productsreactants

5 - 32Chemistry for Allied Health: Equilibrium Figure 9.11 [C]c [D]d[A]a [B]b[C]c [D]d[A]a [B]b K eq = aA + bB cC + dD productsreactants Equilibrium constant (K)

5 - 33Chemistry for Allied Health: Equilibrium N 2(g) + 3 H 2(g) 2 NH 3(g) K eq = [ NH 3 ] 2 [ N 2 ] [ H 2 ] 3 Equilibrium constant (K)

5 - 34Chemistry for Allied Health: Equilibrium Le Chatelier’s principle Stress causes shift in equilibrium Adding or removing reagent N 2(g) + 3 H 2(g) 2 NH 3(g) Stress causes shift in equilibrium Adding or removing reagent N 2(g) + 3 H 2(g) 2 NH 3(g) Add more N 2 ? N2N2N2N2 Reaction shifts to the right [ NH 3 ] inc, [H 2 ] dec

5 - 35Chemistry for Allied Health: Equilibrium Le Chatelier’s principle Adding or removing reagent N 2(g) + 3 H 2(g) 2 NH 3(g) Adding or removing reagent N 2(g) + 3 H 2(g) 2 NH 3(g) Add more NH 3 ? NH 3 Reaction shifts to the left N 2 [ N 2 ] and [H 2 ] inc

5 - 36Chemistry for Allied Health: Equilibrium Le Chatelier’s principle Adding Pressure affects an equilibrium with gases N 2(g) + 3 H 2(g) 2 NH 3(g) P Add P? Increasing pressure causes the equilibrium to shift to the side with the least moles of gas. 4 mol of reactants 2 mol of products

5 - 37Chemistry for Allied Health: Equilibrium Le Chatelier’s principle Temperature can also have an effect. exothermic For exothermic reactions reactants products + heat Raising the temperature shifts it to the left. endothermic For endothermic reactions heat + reactants products Raising the temperature shifts it to the right.

5 - 38Chemistry for Allied Health: Equilibrium Fe 3+ + SCN - FeSCN 2+ Iron and thiocyanide are in equilibrium with the ferrocyanide ion. 1. What happens when Fe 3+ is added ? 2. What happens when SCN - is added ? 3. What happens when Fe 3+ is removed ?

5 - 39Chemistry for Allied Health: Equilibrium FeCl 3 + 3NH 4 CNS Fe(CNS) 3 + 3NH 4 Cl YellowRed FeCl 3 1. What happens when FeCl 3 is added ? NH 4 CNS 2. What happens when NH 4 CNS is added ? Fe(CNS) 3 3. What happens when Fe(CNS) 3 is removed ? Le Chatelier’s principle

5 - 40Chemistry for Allied Health: Equilibrium Figure 9.12

5 - 41Chemistry for Allied Health: Equilibrium Figure 9.13

5 - 42Chemistry for Allied Health: Equilibrium Example O 2 transport in blood Equilibrium equation HbO 2 Hb(O 2 ) 4 Hb + 4 O 2 Hb(O 2 ) 4 abundance of O 2 lungs = abundance of O 2 : Inc lack of O 2 Cells = lack of O 2 : Dec

5 - 43Chemistry for Allied Health: Equilibrium Example O 2 transport in blood Equilibrium equation HbO 2 Hb(O 2 ) 4 Hb + 4 O 2 Hb(O 2 ) 4 Equilibrium expression K Hb = [Hb(O 2 ) 4 ] [Hb] [O 2 ] 4

5 - 44Chemistry for Allied Health: Equilibrium lungs = abundance of O 2 : Example O 2 transport in blood Hb + 4 O 2 Hb(O 2 ) 4 Cells = lack of O 2 : Oxygen is given up by the hemoglobin. Oxygen is picked up by the hemoglobin. (Hypoxia) : 50% more red blood cells in persons living at high altidudes.

5 - 45Chemistry for Allied Health: Equilibrium O 2 transport K Hb = [Hb(O 2 ) 4 ] [Hb] [O 2 ] 4 = 5.0 x10 5 Lets say that [Hb(O 2 ) 4 ] [Hb] K Hb x [O 2 ] 4 = The ratio of oxygenated to unoxygenated hemoglobin is:

5 - 46Chemistry for Allied Health: Equilibrium O 2 transport If the solubility of O 2 in blood at 37 o C = 0.1M. (in the lungs) [Hb(O 2 ) 4 ] [Hb] = = 5.0x10 5 x = 50 [Hb(O 2 ) 4 ] [Hb] = = 5.0x10 5 x = 5.0 x In the capillaries, the O 2 level is about 0.001M so - K Hb x [O 2 ] 4 K Hb x [O 2 ] 4