6. Which expression correctly describes the equilibrium constant for the following reaction? 4NH 3 (g) + 5O 2 (g) 4NO(g) + 6H 2 O(g)

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1 1. Which of the following can we predict from an equilibrium constant for a reaction? 1. The extent of a reaction 2. Whether the reaction is fast or slow 3. Whether a reaction is exothermic or endothermic [A] 1 only [B] 2 only [C] 3 only [D] 1 and 2 only [E] 1 and 3 only 2. A mixture of nitrogen and hydrogen was allowed to come to equilibrium at a given temperature. 3H 2 + N 2 2NH 3 An analysis of the mixture at equilibrium revealed 2.0 mol N 2, 3.0 mol H 2, and 1.5 mol NH 3. How many moles of H 2 were present at the beginning of the reaction? [A] 3.0 [B] 4.0 [C] 4.5 [D] 5.3 [E] For the reaction NO(g) O 2 (g) NO 2 (g) at 750 C, the equilibrium constant K c equals [A] 1.0. [B] K p (RT) 3/2. [C] K p (RT) 3/2. [D] K p (RT) 2/3. [E] K p (RT) 1/2. 4. The equilibrium constant at 1300 K for the reaction H 2 (g) + Br 2 (g) 2HBr(g) is The value of K for HBr(g) 1/2 H 2 (g) + 1/2 Br 2 (g) is [A] [B] [C] [D] [E] Sulfur dioxide combines with O 2 in the presence of a catalyst as represented by the equation 2SO 2 (g) + O 2 (g) 2SO 3 (g) If the equilibrium is established by adding 0.10 mol each of SO 2 and O 2 to a 1-L vessel, then which of the following must be true at equilibrium? [A] [SO 2 ] = [O 2 ] [B] [SO 2 ] = [O 2 ] = [SO 3 ] [C] [O 2 ] = 2[SO 3 ] [D] [SO 2 ] > [O 2 ] [E] [SO 2 ] < [O 2 ] 6. Which expression correctly describes the equilibrium constant for the following reaction? 4NH 3 (g) + 5O 2 (g) 4NO(g) + 6H 2 O(g) [A] K c = 4 [ N H 3 ]+ 5[ O 2 ] 6 O ]+ 4[ NO] [D] K c = O ] 6 + NO NH 3 [ ] 4 [E] K [ ] 4 + [ O 2 ] 5 c = [B] K c = 6 O ]+ 4[ NO] 4[ NH 3 ]+ 5[ O 2 ] [ NH 3 ] 4 + [ O 2 ] 5 O ] 6 + NO [ ] 4 [C] K c = O ]+ [ NO] [ NH 3 ]+ [ O 2 ]

2 7. The equilibrium constant, K c, for the reaction 1 2 N 2 O 4 (g) NO 2 (g) is 3.3 at 100 C. The value for the equilibrium constant will be changed if 1. concentrations are given in atmospheres instead of moles per liter. 2. the temperature is changed to 200 C. 3. the equation above is doubled. [A] 1 only [B] 2 only [C] 1 and 2 only [D] 2 and 3 only [E] 1, 2, and 3 8. In an experiment, mol H 2 and mol I 2 are mixed in a 1.00-L container, and the reaction forms HI. If K c = 49. for this reaction, what is the equilibrium concentration of HI? I 2 (g) + H 2 (g) 2HI(g) [A] M [B] 0.18 M [C] 0.31 M [D] 0.62 M [E] 0.83 M 9. Consider the reaction S 2 Cl 2 (l) + CCl 4 (l) CS 2 (g) + 3Cl 2 (g) DH = 84.3 kj If the above reactants and products are contained in a closed vessel and the reaction system is at equilibrium, the number of moles of CS 2 can be increased by [A] adding some S 2 Cl 2 to the system. [C] increasing the size of the reaction vessel. [D] decreasing the temperature of the reaction system. [E] adding some CCl 4 to the system. [B] adding some Cl 2 to the system. 10. For the following reaction system at equilibrium, which one of the changes would cause the equilibrium to shift to the right? Br 2 (g) + 2NO(g) 2NOBr(g) DH = 30 kj [A] Increase the volume of the reaction vessel. [B] Remove some NO. [C] Add some NOBr. [D] Remove some Br 2. [E] Decrease the temperature. 11. When phosphorus pentachloride is made by the reaction of PCl 3 (g) and Cl 2 (g) at 240 C, K c =20. PCl 3 (g) + Cl 2 (g) PCl 5 (g) If pure PCl 5 is placed in a 1.00-L container and allowed to come to equilibrium and the equilibrium concentration of PCl 5 (g) is mol/l, then the concentration of PCl 3 (g) is [A] M. [B] M. [C] M. [D] M. [E] M.

3 12. If the system NH 4 Cl(s) NH 3 (g) + HCl(g) is at equilibrium at constant temperature and the volume of the vessel is doubled, when the system comes to equilibrium, 1. the amount of NH 3 and HCl is doubled. 2. the partial pressure of NH 3 and HCl in the vessel remains unchanged. 3. the number of moles of NH 4 Cl decreases. [A] 1 only [B] 2 only [C] 3 only [D] 1 and 3 only [E] 1, 2, and Carbon disulfide and chlorine react according to the following equation: CS 2 (g) + 3Cl 2 (g) S 2 Cl 2 (g) + CCl 4 (g) When 1.00 mol of CS 2 and 4.00 mol of Cl 2 are placed in a 2.00-L container and allowed to come to equilibrium, the mixture is found to contain mol of CCl 4. How many moles of Cl 2 are present at equilibrium? [A] 0.75 [B] 1.50 [C] 2.50 [D] 2.75 [E] mol of NOCl is placed in a 1.00-L reaction vessel at 700 K, and after the system comes to equilibrium, the concentration of NOCl is M. Calculate the equilibrium constant K c for the reaction 2NOCl(g) 2NO(g) + Cl 2 (g) [A] [B] [C] [D] [E] Solid HgO, liquid Hg, and gaseous O 2 are placed in a glass bulb and are allowed to reach equilibrium at a given temperature. 2HgO(s) + heat 2Hg(l) + O 2 (g) The amount of Hg(l) in the bulb could be increased by 1. removing some HgO. 2. removing some O increasing the temperature. [A] 1 only [B] 2 only [C] 3 only [D] 1 and 2 only [E] 2 and 3 only 16. For which of the following systems at equilibrium and at constant temperature will decreasing the volume cause the equilibrium to shift to the right? [A] N 2 (g) + 3H 2 (g) 2NH 3 (g) [B] 2H 2 O(g) 2H 2 (g) + O 2 (g) [C] 2NO 2 (g) 2NO(g) + O 2 (g) [D] NH 4 Cl(s) NH 3 (g) + HCl(g) [E] H 2 (g) + Cl 2 (g) 2HCl(g) 17. Which of the following can we determine by using an equilibrium constant for a gaseous reaction system? 1. the effect of changing the volume of the reaction system 2. the extent of a reaction at equilibrium 3. the direction of a reaction upon adding both reactants and products [A] 1 only [B] 2 only [C] 3 only [D] 1 and 2 only [E] 1, 2, and 3

4 18. Dinitrogen tetroxide readily undergoes decomposition to form red-brown NO 2 (g), as represented by the equation N 2 O 4 (g) 2NO 2 (g) At 25 C, 0.11 mol N 2 O 4 reacts to form 0.10 mol N 2 O 4 and 0.02 mol NO 2. At 90 C, 0.11 mol N 2 O 4 forms mol N 2 O 4 and 0.12 mol NO 2. From these data, we can conclude that 1. N 2 O 4 molecules react by a first-order rate law. 2. the reaction is endothermic. 3. the equilibrium constant for the reaction increases with an increase in temperature. [A] 1 only [B] 2 only [C] 3 only [D] 1 and 2 only [E] 2 and 3 only 19. 2NO(g) + 3F 2 (g) 2F 3 NO(g) Suppose the above equilibrium is established by adding 0.20 mol NO and 0.30 mol F 2 to a 5.0-L container. If y moles of F 3 NO are present at equilibrium, then the number of MOLES of fluorine remaining at equilibrium will be [A] 0.30 y. [B] 0.20 y. [C] y. [D] y. [E] y. 20. Exactly 1.0 mol N 2 O 4 is placed in an empty 1.0-L container and is allowed to reach equilibrium described by the equation N 2 O 4 (g) 2NO 2 (g). If at equilibrium the N 2 O 4 is 40.% dissociated, what is the value of the equilibrium constant (in units of moles per liter) for the reaction under these conditions? [A] 0.20 [B] 0.84 [C] 1.1 [D] 1.5 [E] The reaction of carbon monoxide and diiodine pentoxide as represented by the equation I 2 (g) + 5CO 2 (g) 5CO(g) + I 2 O 5 (g) is exothermic. The yield could be increased by [A] increasing the pressure. [C] increasing the temperature. [E] decreasing the volume of the reaction vessel. [B] decreasing the pressure. [D] decreasing the temperature. 22. For the reaction system N 2 (g) + 3H 2 (g) 2NH 3 (g) at equilibrium, DH is 92 kj. In order to both shift the equilibrium and increase the yield of ammonia, we should 1. increase the temperature. 2. decrease the temperature. 3. increase the pressure. 4. decrease the pressure. [A] 1 only [B] 2 only [C] 1 and 3 only [D] 2 and 3 only [E] 1 and 4 only

5 23. The equilibrium constant for the reaction H 2 (g) + I 2 (g) 2HI(g) is 62.5 at 800 K. What is the equilibrium concentration of I 2 if [HI] = 0.20 M and [H 2 ] = 0.10 M? [A] M [B] M [C] 0.20 M [D] 0.10 M [E] M 24. For the reaction system CoO(s) + H 2 (g) Co(s) + H 2 O(g) at 550 C, K = 67. The equilibrium constant expression is [A] [ ] [ ]. [B] [ Co] O] [ CoO] ]. [C] [ Co] O] ] [ CoO] H 2 Co [ ] H 2 O. [D] ] [ ] [ ]. O]. [E] H 2 O H For the reaction system 2HI(g) H 2 (g) + I 2 (g) K c = at 720 K. If the initial concentrations of HI, H 2, and I 2 are all M at 720 K, which one of the following statements is CORRECT? [A] The system is at equilibrium. [B] The concentrations of HI and I 2 will increase as the system is approaching equilibrium. [C] The concentrations of H 2 and HI will decrease as the system is approaching equilibrium. [D] The concentration of HI will increase as the system is approaching equilibrium. [E] The concentrations of H 2 and I 2 will increase as the system is approaching equilibrium.