b. Calculate the value of the equilibrium constant at 127ºC for the reaction 2NH 3 (g) N 2 (g) + 3H 2 (g)

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1 1. Write the equilibrium expression for the following reaction: 4NH 3 (g) + 7O 2 (g) 4NO 2 (g) + 6H 2 O(g) 2. The following equilibrium concentrations were observed for this reaction at 127ºC: N 2 (g) + 3H 2 (g) 2NH 3 (g) [NH 3 ] = 3.1 x 10-2 mol/l [N 2 ] = 8.5 x 10-1 mol/l [H 2 ] = 3.1 x 10-3 mol/l a. Calculate the value of K at 127ºC for this reaction. b. Calculate the value of the equilibrium constant at 127ºC for the reaction 2NH 3 (g) N 2 (g) + 3H 2 (g) c. Calculate the value of the equilibrium constant at 127ºC for the reaction given by the equation 1/2N 2 (g) + 3/2H 2 (g) NH 3 (g) 3. The following results were collected for two experiments involving the reaction at 600ºC between gaseous sulfur dioxide and oxygen to form gaseous sulfur trioxide: Rxn: 2SO 2 (g) + O 2 (g) 2SO 3 (g) Experiment 1 Experiment 2 Initial Equilibrium Initial Equilibrium [SO 2 ] 0 = 2.00 M [SO 2 ] = 1.50 M [SO 2 ] 0 = M [SO 2 ] = M [O 2 ] 0 = 1.50 M [O 2 ] = 1.25 M [O 2 ] 0 = 0 [O 2 ] = M [SO 3 ] 0 = 3.00 M [SO 3 ] = 3.50 M [SO 3 ] 0 = M [SO 3 ] = M Show that the equilibrium constant is the same in both cases. 4. The reaction for the formation of nitrosyl chloride 2NO(g) + Cl 2 (g) 2NOCl(g) was studied at 25ºC. The pressures at equilibrium were found to be P NOCl = 1.2 atm P NO = atm PCl 2 = atm Calculate the value of K p for this reaction at 25ºC.

2 5. Using the value of K p obtained in #4,calculate the value of K c at 25ºC for the reaction 2NO(g) + Cl 2 (g) 2NOCl(g) 6. Write the expressions for K c and K p for the following process: a. The decomposition of solid phosphorus pentachloride to liquid phosphorus trichloride and chlorine gas. Rxn: PCl 5 (s) PCl 3 (l) + Cl 2 (g) b. Deep blue solid copper(ii) sulfate pentahydrate is heated to drive off water vapor to form white solid copper(ii) sulfate. Rxn: CuSO 4 5H 2 O(s) CuSO 4 (s) + 5H 2 O(g) 7. For the synthesis of ammonia at 500ºC, the equilibrium constant is L 2 /mol 2. Rxn: N 2 (g) + 3H 2 (g) 2NH 3 (g) Predict the direction in which the system will shift to reach equilibrium in each of the following cases: a. [NH 3 ] 0 = M; [N 2 ] 0 = 1.0 x 10-5 M; [H 2 ] 0 = M b. [NH 3 ] 0 = M; [N 2 ] 0 = 1.50 x 10-5 M; [H 2 ] 0 = M c. [NH 3 ] 0 = M; [N 2 ] 0 = 5.0 M; [H 2 ] 0 = M 8. Dinitrogen texroxide in its liquid state was used as one of the fuels on the lunar lander for the NASA Apollo missions. In the gas phase it decomposes to gaseous nitrogen dioxide: N 2 O 4 (g) 2NO 2 (g) Consider an experiment in which gaseous N 2 O 4 was placed in a flask and allowed to reach equilibrium at a temperature where K p = atm. At equilibrium, the pressure of N 2 O 4 was found to be 2.71 atm. Calculate the equilibrium pressure of NO 2 (g).

3 9. At a certain temperature a 1.00-L flask initially contained mol PCl 3 (g) and 8.70 x 10-3 mol PCl 5 (g). After the system had reached equilibrium, mol Cl 2 (g) was found in the flask. Gaseous PCl 5 decomposes according to the reaction PCl 5 (g) PCl 3 (g) + Cl 2 (g) Calculate the equilibrium concentrations of all species and the value of K c. 10. Carbon monoxide reacts with steam to produce carbon dioxide and hydrogen. At 700 K the equilibrium constant is Calculate the equilibrium concentrations of all species if mol of each component is mixed in a L flask. Rxn: CO(g) + H 2 O(g) H 2 (g) + CO 2 (g) 11. Assume that the reaction for the formation of gaseous hydrogen fluoride from hydrogen and fluorine has an equilibrium constant of at a certain temperature. In a particular experiment, mol of each component was added to a L flask. Calculate the equilibrium concentrations of all species. Rxn: H 2 (g) + F 2 (g) 2HF(g) 12. Assume that gaseous hydrogen iodide is synthesized from hydrogen gas and iodine vapor at a temperature where the equilibrium constant is 1.00 x Suppose HI at x 10-1 atm, H 2 at atm, and I 2 at x 10-3 atm are mixed in a L flask. Calculate the equilibrium pressures of all species. Rxn: H 2 (g) + I 2 (g) 2HI(g)

4 13. Gaseous phosphorus pentachloride decomposes to gaseous phosphorus trichloride and chlorine at a temperature where K c = mol/l. Suppose 2.00 mol of phosphorus pentachloride in a 2.00-L vessel is allowed to come to equilibrium. Calculate the equilibrium concentrations of all species. Rxn: PCl 5 (g) PCl 3 (g) + Cl 2 (g) Text problem worth looking at: 21) A sample of gaseous PCl 5 was introduced into an evacuated flask so that the pressure of pure PCl 5 would be 0.50 atm at 523 K. However, PCl 5 decomposes to gaseous PCl 3 and Cl 2, and the actual pressure in the flask was found to be 0.84 atm. Calculate K p for the decomposition reaction PCl 5 (g) PCl 3 (g) + Cl 2 (g) at 523 K. Calculate K c at this temperature. Others: For the reaction C(s) + CO 2 (g) 2CO(g), K c = 1.6. What is the equilibrium concentration of CO if the equilibrium concentration of CO 2 is 0.50 M? Calculate the equilibrium partial pressure of BCl 3 in a 2.00 L container that was evacuated, then charged with 4.29 g of PH 3 BCl 3 and allowed to come to equilibrium according to the equation PH 3 BCl 3 (s) PH 3 (g) + BCl 3 (g). The value of K p for this reaction is

5 For the reaction 2ICl(g) I 2 (g) + Cl 2 (g), K c at 25 C is Calculate the equilibrium concentration (in mol/l) of Cl 2 (g) if the initial concentration of ICl(g) is 1.33 mol/l. There is no I 2 or Cl 2 initially present. 14. Arsenic can be extracted from its ores by first reacting the ore with oxygen (called roasting) to form solid As 4 O 6, which is then reduced using carbon: As 4 O 6 (s) + 6C(s) As 4 (g) + 6CO(g) Predict the direction of the shift of the equilibrium position in response to each of the following changes in conditions: a. Addition of carbon monoxide b. Addition or removal of carbon or tetraarsenic hexoxide (As 4 O 6 ) c. Removal of gaseous arsenic (As 4 ) 15. Predict the shift in equilibrium position that will occur for each of the following processes when the volume is reduced. a. The preparation of liquid phosphorus trichloride by the reaction P 4 (s) + 6Cl 2 (g) 4PCl 3 (l) b. The preparation of gaseous phosphorus pentachloride according to the equation PCl 3 (g) + Cl 2 (g) PCl 5 (g) c. The reaction of phosphorus trichloride with ammonia: PCl 3 (g) + 3NH 3 (g) P(NH 2 ) 3 (g) + 3HCl(g)

6 16. For each of the following reactions, predict how the value of K changes as the temperature is increased. a. N 2 (g) + O 2 (g) 2NO(g) ΔHº = 181 kj b. 2SO 2 (g) + O 2 (g) 2SO 3 (g) ΔHº = 198 kj Text problems worth looking at: 33) An important reaction in the commercial production of hydrogen is CO(g) + H 2 O(g) H 2 (g) + CO 2 (g) ΔH = 41 kj How will this system at equilibrium shift in each of the four following cases? How is the value of K affected? a. Gaseous carbon dioxide is removed. b. Water vapor is added. c. The pressure is increased by adding helium gas. d. The temperature is increased. 34) What will happen to the number of moles of SO 3 in equilibrium with SO 2 and O 2 in the reaction 2SO 3 (g) 2SO 2 (g) + O 2 (g) ΔHº = 197 kj in each of the following cases? How is the K value affected? a. Oxygen is added. b. The pressure is increased by decreasing the volume. c. The pressure is increased by adding argon gas. d. The temperature is decreased. e. A catalyst is added. f. Gaseous sulfur dioxide is removed.