3 A (aq) + 2 D (aq) + 5 C (s) <==> 3 B (aq) + 4 E (aq) + 2 G (ppt)

Transcription

1 AP Chemistry Test (Chapter 13) Multiple Choice (30%) 1) Which one best describes the K C for this reaction? 3 A (aq) + 2 D (aq) + 5 C (s) <==> 3 B (aq) + 4 E (aq) + 2 G (ppt) A) K c = [A] 3 [D] 2 B) K c = [B] 3 [E] 4 [G] 2 [E] 4 [D] 2 [A] 3 [D] 2 [C] 5 C) K c = [E] 4 [B] 3 D) K c = [A] 3 [D] 2 [C] 5 [A] 3 [D] 2 [B] 3 [E] 4 [G] 2 E) None of these is correct 2) Please consider the gas phase reaction: 2 NH 3 (g) <==> 3 H 2 (g) + N 2 (g) H = +345 kj/mol Which one would decrease the yield of H 2? A) High T & high P B) Low T & low P C) High T & low P D) Low T & high P 3) AlBr 3 dissolves in water, according to this mechanism: AlBr 3 (s) <==> Al +3 (aq) + 3 Br (aq) What effect would the addition of Na 3 PO 4 have on this equilibrium? A) Q becomes larger & the reaction creates more products. B) Q becomes larger & the reaction creates more reactants. C) Q becomes smaller & the reaction creates more products. D) Q becomes smaller & the reaction creates more reactants. E) There is no net effect on the equilibrium position. 4) Based upon the following information, which one is true about the reaction mixture? 2 NH 3 (g) <==> N 2 (g) + 3 H 2 (g) K P = 0.88 P (NH 3 ) = 2.19 atm P (N 2 ) = 4.33 atm P (H 2 ) = 0.72 atm A) The product concentrations are too high & the reaction will shift left to establish B) The product concentrations are too high & the reaction will shift right to establish C) The reactant concentrations are too high & the reaction will shift right to establish D) The reactant concentrations are too high & the reaction will shift left to establish

2 5) Which one will occur if the volume of the container is decreased. 2 A (l) + 5 B (g) <==> 2 C (g) + 4 D (ppt) + 2 E (g) H = +545 kj/mol rxn Kp = 35.2 A) The mass of A will remain constant. B) The temperature will decrease. C) The partial pressure of B will increase. D) The mass of D will increase. E) None of these 6) Consider the gaseous equilibrium: 2 A B + 3 C. Determine the value of the missing [C] at Experiment # [A] at equilibrium [B] at equilibrium [C] at equilibrium M 0.30 M 0.20 M M 0.20 M??? A) 0.32 M B) M C) 0.13 M D) 0.70 M E) None of these are correct. 7) Which one is false about this graph? [M] D E Time A) The reaction is spontaneous in the forward direction. B) The reaction is product favored at C) Kc > 1 D) E <==> D E) None of these are false. 8) If this system is at equilibrium in a closed vessel and a small amount of HN 3 is added, which one would NOT happen? HN 3 (g) + 2 H 2 O (l) <==> N 2 H 4 (g) + HNO 2 (g) H = 545 kj/mol rxn A) The partial pressure of HNO 2 would increase to re-establish B) The partial pressure of HN 3 would decrease to re-establish C) Some N 2 H 4 would form to re-establish D) The inside of the flask would have water droplets forming on it. E) The temperature would increase.

3 9) K C = 1.05 X 10 4 for this reaction: 2 Fe 3+ (aq) + 3 S 2 (aq) <==> Fe 2 S 3 (ppt) The concentration of Fe 3+ in equilibrium with M S 2 is. A) 9.23 M B) M C) M D) M E) None of these are correct. 10) If the reaction flask is placed into an ice water bath, which one will occur? 2 A (g) + 3 B (g) <==> C (g) + 4 D (s) + E (g) H = +671 kj/mol rxn A) The total pressure in the flask will increase. B) The molarity of C will increase. C) The partial pressure of A will decrease. D) The mass of D will remain constant. E) None of these will occur. 11) Please consider the following process. Which one is true? Reactants < == > Products Kc 1 = Kc in forward reaction progress. Kc 2 = Kc in reverse reaction progress. A) Kc 1 = 1/Kc 2 B) Kc 1 = Kc 2 C) Kc 1 = Kc 2 D) Kc 1 = (Kc 2 ) 2 E) No relationship exists between Kc 1 and Kc 2. 12) Please choose all that will cause a decrease in Kc. I) Heating an exothermic reaction. II) Heating an endothermic reaction. III) Placing a reaction with H in an ice bath. IV) Placing a reaction with + H in an ice bath. A) II, III B) I, IV C) I, II, III, IV D) I, III E) II, IV 13) Please consider this reaction. 4 PBr 3 (g) + 6 Cl 2 (g) <==> 4 PCl 3 (g) + 6 Br 2 (g) Kp = What is the Kp for this reaction? 2 PCl 3 (g) + 3 Br 2 (g) <==> 2 PBr 3 (g) + 3 Cl 2 (g) A) B) C) 10.0 D) 2.24 E) None of these are correct.

4 14) Which one is an example of a chemical or physical process with Kc < 1 at 1 atm. A) A match burning. B) Ice melting at 10 o C. C) Water boiling at 100 o C. D) Leaves growing in the summer. 15) Please choose all that apply to a nonspontaneous reaction. I) Kc > 1 for the reverse reaction. II) Kc < 1 for the forward reaction. III) The concentrations of products are greater than the reactants at IV) The concentrations of reactants are greater than the products at A) IV B) III C) I, II, III D) I, II, IV E) None of these choices apply. Problems (70%) 1) 2 NaHCO 3 (s) <===> Na 2 CO 3 (s) + H 2 O (g) + CO 2 (g) A g sample of solid NaHCO 3 was placed in a previously evacuated rigid 8.00-liter container and heated to C. Some of the original solid remained and the total pressure in the container was 4.46 atmospheres when equilibrium was reached. a) How many grams of the original solid remained in the container? b) Write the equilibrium expression for the equilibrium constant, K p, and calculate its value. 2) N 2 O 4 (g) <===> 2 NO 2 (g) a) At a temperature of 342 K, 1.25 mole of gaseous N 2 O 4 is placed in a 4.00-liter flask, and equilibrium for the reaction is attained when % of the N 2 O 4 has decomposed. Write the equilibrium expression and calculate the value of the equilibrium constant K c for the reaction. b) What is Kp for the reverse reaction at 342 K? c) At the same temperature, 0.52 mole NO 2 and 0.10 mole N 2 O 4 are placed in a different liter flask. When equilibrium is established, is there more of less than 0.10 mole N 2 O 4 present? Justify your answer. 3) 2 Au 3+ (aq) + 3 SO 4 2 (aq) < == > Au 2 (SO 4 ) 3 (ppt) Kc = 8.00 X 10 3 a) When enough solid Au 2 (SO 4 ) 3 is added to 1.00 L of water to form a saturated solution, what will be the concentrations of Au 3+ and SO 4 2? b) What will happen to the concentration of Au 3+ when a solution of Pb(NO 3 ) 2 is slowly poured into the 1.00-L flask at equilibrium? Please support your answer.

5 4) 2 HCl (g) < == > H 2 (g) + Cl 2 (g) Kp = 2.70 A 2.00-L flask at 315 K is injected with 1.00 atm HCl. a) What is the partial pressure of HCl at equilibrium? b) How many moles of HCl decomposed? 5) Please add to the graph on the answer sheet what would occur if F 2 is removed from the reaction flask after equilibrium was reached. O2 (g) + 2 F2 (g) <==> 2 OF2 (g)

6 Test (Chapter 13) Name 1) 6) 11) 2) 7) 12) 3) 8) 13) 4) 9) 14) 5) 10) 15) [O 2 ] and [F 2 ] 5) F 2 is removed. O 2 is added. [OF 2 ] Time