11 Equilibrium. S T A T I O N 1 K e q E X P R E S S I O N S S T A T I O N 2 G R A P H S. South Pasadena Honors Chemistry 11 Equilibrium Period Date

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1 South Pasadena Honors Chemistry Name 11 Equilibrium Period Date S T A T I O N 1 K e q E X P R E S S I O N S Write the expression for the equilibrium constant for the reaction: Fe 3+ (aq) + SCN (aq) FeSCN 2+ (aq) Write the expression for the equilibrium constant for the reaction: Fe 3O 4 (s) + 4 H 2 (g) 3 Fe (s) + 4 H 2O (g) Write the expression for the equilibrium constant for the reaction: Ca(OH) 2 (s) Ca 2+ (aq) + 2 OH (aq) The equilibrium constant, K eq, for a particular reaction is Is this equilibrium system reactant or productfavored? Explain briefly. 11 Equilibrium S T A T I O N 2 G R A P H S Consider the graph for the following reaction: CO 2 (g) + H 2 (g) CO(g) + H 2O (g) At what time does this system reach equilibrium? Is this equilibrium reactant-favored or product-favored? Write the equilibrium expression and calculate the value of K eq. If the reaction mixture contained 0.50 M CO 2, 0.50 M H 2, 0.50 M CO, and 0.50 M H 2O, in which direction will the reaction proceed? Justify your answer with a calculation of Q.

2 Station 1 Self-Assessment Objective: Write the equilibrium constant of a chemical equation. Objective: Describe the relative amounts of substances of a system at equilibrium using the magnitude of the value of the equilibrium constant. Station 2 Self-Assessment Objective: Describe what is observed when a system reaches equilibrium. Objective: Describe the relative amounts of substances of a system at equilibrium using the magnitude of the value of the equilibrium constant. Objective: Determine whether a reversible reaction proceeds toward the right or the left by comparing the reaction quotient Q to K eq.

3 11 Equilibrium S T A T I O N 3 S T R E N G T H O F A C I D S For each of the following acids, write the expression for the equilibrium constant. Acid Equation K eq Equilibrium Expression Hypochlorous acid, HOCl HOCl(aq) H + (aq) + OCl (aq) Nitrous acid, HNO 2 HNO 2(aq) H + (aq) + NO 2 (aq) Lactic Acid, HC 3H 5O 3 HC 3H 5O 3(aq) H + (aq) + C 3H 5O 3 (aq) Hydrocyanic acid, HCN HCN(aq) H + (aq) + CN (aq) List the acids from weakest to strongest: < < < 11 Equilibrium S T A T I O N 4 I C E B O X P R O B L E M Consider the equilibrium: 2 SO 2 (g) + O 2 (g) 2 SO 3 (g) If mol SO 3(g) is placed a L container, it is found that mole of O 2(g) is in the container at equilibrium. Fill in the ICE box and determine the K eq for this reaction. 2 SO 2 (g) + O 2 (g) 2 SO 3 (g) Initial Change Equilibrium

4 Station 3 Self-Assessment Objective: Find the amounts of each substance in a reaction mixture at equilibrium given initial amounts and value of K using an ICE Chart. Station 4 Self-Assessment Objective: Find the amounts of each substance in a reaction mixture at equilibrium given initial amounts and value of K using an ICE Chart.

5 11 Equilibrium S T A T I O N 5 A N O T H E R I C E B O X P R O B L E M At 985 C, the equilibrium constant, K eq, for the reaction, H 2 (g) + CO 2 (g) H 2O (g) + CO (g), is If 2.00 moles each of H 2(g) and CO 2(g) are placed in a 1.00 L container and allowed to come to equilibrium, determine the equilibrium concentrations of the four chemicals. Initial H 2 (g) + CO2 (g) H2O (g) + CO (g) Change Equilibrium 11 Equilibrium S T A T I O N 6 O N E M O R E I C E B O X P R O B L E M Consider the reaction: NH 3 (aq) + H 2O + (l) NH 4 (aq) + OH (aq) K eq = What is the [OH ] in a M solution of NH 3 (aq) when it reaches equilibrium? Initial NH 3 (aq) + H 2O (l) NH 4 + (aq) + OH (aq) Change Equilibrium

6 Station 5 Self-Assessment Objective: Find the amounts of each substance in a reaction mixture at equilibrium given initial amounts and value of K using an ICE Chart. Station 6 Self-Assessment Objective: Find the amounts of each substance in a reaction mixture at equilibrium given initial amounts and value of K using an ICE Chart.

7 11 Equilibrium S T A T I O N 7 L E C H A T D E M O N S T R A T I O N S Consider the equilibrium: 2 H + 2 (aq) + 2 CrO 4 (aq) Cr 2O 2 7 (aq) + H 2O (l) (yellow) (orange) What color shift would be observed when a solution of concentrated NaOH is added? (NaOH removes H + from the system.) Consider the equilibrium: 2 NO 2 (g) N 2O 4 (g) (amber) (colorless) When this equilibrium system is placed in a cold dry ice-acetone bath, the color disappears. Is this reaction endothermic or exothermic? Consider the equilibrium: Co(NH 3) 2+ 6 (aq) + 4 Cl (aq) CoCl 4 (aq) + 6 H 2O (l) (pink) (blue) A solution of silver nitrate is added to this equilibrium. What is the stress? (silver nitrate removes Cl from the system.) What color shift would be observed when the silver nitrate solution is added? Placing this equilibrium system in hot water turns the mixture blue. Is heat a reactant or a product? 11 Equilibrium S T A T I O N 8 L E C H Â T E L I E R S P R I N C I P L E Consider the gaseous equilibrium: 2 CCl 4(g) + O 2(g) + heat 2 COCl 2(g) + 2 Cl 2(g) Predict the effect each change would have on the concentrations of each substance. [CCl 4] [O 2] Shift [COCl 2] [Cl 2] Add CCl 4 Remove Cl 2 Add COCl 2 Increase temperature Reduce container volume Add a catalyst Remove O 2 A different equilibrium shifts toward the reactants when the temperature is increased. From this observation, you know that the reaction is (exothermic / endothermic).

8 Station 7 Self-Assessment Objective: Predict the direction a reaction will shift and how the amounts of substances in the reaction mixture will change if reactants/products are added/removed, the pressure/volume of a gas sample is changed, or if the temperature is changed. Station 8 Self-Assessment Objective: Predict the direction a reaction will shift and how the amounts of substances in the reaction mixture will change if reactants/products are added/removed, the pressure/volume of a gas sample is changed, or if the temperature is changed.

9 11 Equilibrium S T A T I O N 9 P R A C T I C E P R O B L E M S

10 Station 9 Self-Assessment Objective: Predict the direction a reaction will shift and how the amounts of substances in the reaction mixture will change if reactants/products are added/removed, the pressure/volume of a gas sample is changed, or if the temperature is changed. Objective: Describe how to maximize the yield of a product by shifting a reversible reaction.