Chemistry Chapter 14 Chemical Equilibrium Part 1

Chem Chapter 14: Chemical Equilibrium1. The value of the equilibrium constant for the reaction: 2 HBr(g) <----> H2(g) + Br2(g) is Kc = 1.26 x 10-12 at 500 K. This implies that: a) the product concentrations will be large relative to the reactants at equilibrium. b) the reaction has a large negative ΔG°. c) the rate of this reaction is very slow. d) the reactants are much more thermodynamically stable than the products. 2. Given the information in Problem #1, what would be the value of the equilibrium constant K'c for the related reaction written in the following fashion? 1/2 H2(g) + 1/2 Br2(g) <---> HBr(g) a) 7.9 x 1011 b) 8.9 x 105 c) 1.1 x 10-6 d) 1.26 x 10-12 3. Based on the information in Problem #1, what will be the corresponding value of Kp, the pressure form of the equilibrium constant? (R = 0.08206 Latm/mol K) a) 5.17 x 10-12 b) 1.26 x 10-12 c) 3.07 x 10-13 d) 2.12 x 1011 4. The reversible reaction: 2 SO2(g) + O2 <---> 2 SO3(g) has come to equilibrium in a vessel of specific volume and at a given temperature. Before the reaction, the concentrations of the reactants were 0.060 mol / L of SO2 and 0.050 mol / L of O2. No SO3 was present. After equilibrium was reached, the concentration of SO3 was 0.040 mol / L. What is the equilibrium constant Kc for this reaction? a) 133 b) 4.0 c) 8.88 d) 13.3 5. What would be the effect of decreasing the pressure by increasing the volume on the following system at equilibrium? 2 CO(g) + O2 <---> 2 CO2(g) a) The Kp value would get smaller. b) The Kp value would get larger. c) The equilibrium would be perturbed and would show a net shift to the left. d) The equilibrium would be perturbed and would show a net shift to the right. e) There would be no effect. The system is at equilibrium. 6. A simple unimolecular reaction A <---> B has an equilibrium constant Kc = 2.5. If initially the concentration of A in the reaction vessel is 1.0 M and there is no B present, what will be the concentration of A and B when the system reaches equilibrium? a) [A] = 1.0 M, [B] = 2.5 M b) [A] = 2.5 M, [B] = 1.0 M c) [A] = 0.330 M, [B] = 0.825 M d) [A] = 0.714 M, [B] = 0.286 M e) [A] = 0.286 M, [B] = 0.714 M 7. Nitrogen reacts with hydrogen to form ammonia in the Haber process: N2(g) + 3 H2(g) <---> 2 NH3(g) An equilibrium mixture at a given temperature is found to contain 0.31 mol / L N2, 0.50 mol / L H2, and 0.14 mol / L NH3. Calculate the value of Kc at the given temperature. a) 1.97 b) 0.903 c) 1.107 d) 0.506 8. The equilibrium constant for the reaction: Br2(g) + F2(g) <---> 2 BrF(g) is 54.7. What are the equilibrium concentration of BrF if the initial concentrations of bromine and fluorine were both 0.250 mol / L? a) [BrF] = 0.241 M b) [BrF] = 0.482 M c) [BrF] = 0.00882 M d) 0.25 M e) [BrF] = 0.39 M 9. The reaction: 2 NO2(g) <---> 2 NO(g) + O2(g) is endothermic. If additional O2 is added to a vessel at equilibrium what will ultimately happen to the NO2 concentration? a) it will increase b) it will decrease c) it will remain the same 10. In the reaction in Problem #9, what will happen to the NO(g) concentration after additional O2 is added? a) it will increase b) it will decrease c) it will remain the same 11. In the reaction in Problem #9, what will happen to the NO2(g) concentration if the temperature is increased? a) it will increase b) it will decrease c) it will remain the same 12. The values of the equilibrium constant for the reaction in Problem #1 at two different temperatures are: Kc = 1.26 x 10-12 at T = 500 K Kc = 8.99 x 10-18 at T = 298 K What is the ΔH for this reaction in kJ/mol? (the gas constant R = 8.314 x 103 kJ/mol) a) -69.8 kJ/mol b) 43.7 kJ/mol c) 72.7 kJ/mol d) 134 kJ/mol 13. Given: N2(g) + 3 H2(g) <---> 2 NH3(g) At equilibrium at a certain temperature, the concentration of NH3(g), H2(g) and N2(g) are 0.980 M, 1.53 M and 0.510 M, respectively. Calculate the value of Kc for this reaction. a) 1.26 b) 1.96 c) 3.02 d) 0.526 e) 0.837 14. A large equilibrium constant a) indicates that a reaction has a small rate constant. b) indicates that the reaction favors the formation of reactants. c) indicates that a reaction has a large rate constant. d) indicates that the reaction favors the formation of products. e) results from the addition of a catalyst to a reaction mixture. 15. The value of the equilibrium constant for the following reaction is 3.4 x 105. 2A + B <---> 2C + 4D What is the value of the equilibrium constant for the reaction: C + 2D <---> A + 1/2B a) K = 1.2 x 1011 b) K = 2.9 x 10-6 c) K = 1.7 x 10-3 d) K = 5.8 x 102 e) K = 8.7 x 10-12 16. Consider the following reaction: 4 PCl3(g) --> P4(g) + 6 Cl2(g) If the initial concentration of PCl3(g) is 1.0 M, and "x" is the equilibrium concentration of P4(g), what is the correct equilibrium relation? a) Kc = 6x7 b) Kc = 6x7/(1.0 - x)4 c) Kc = (x)(6x) 6/(1.0 - 4x)4 d) Kc = x7/(1.0 - x)4 e) Kc = 6x7/(1.0 - 4x)4 17. Consider the following reaction. What would be the equilibrium constant expression? 4 Br2(g) + CH4(g) <---> 4 HBr(g) + CBr4(g) a) Kc = ([CBr4][HBr])/([Br2][CH4] b) Kc = ([CBr4][Br2]4)/([HBr]4[CBr4]) c) Kc = ([CBr4][HBr]4)/([Br2]4[CH4]) d) Kc = ([CH4][Br2])/([HBr][CBr4]) e) Kc = ([HBr]4)/([Br2]4[CH4]) 18. Consider the following reaction: H2(g) + I2(g) <---> 2 HI(g) If the value of Kc for this reaction is 25 at 1100 K, and initially only 4.00 M HI(g) is present, what is the equilibrium concentration of I2(g)? a) 2.00 M b) 0.571 M c) 0.148 M d) 0.363 M e) 0.667 M 19. What is the equilibrium constant expression for the reaction below? 2 CaSO4(s) <---> 2 CaO(s) + 2 SO2(g) + O2(g) a) Kc = [CaO]/[CaSO4] b) Kc = [CaO]2[SO2]2[O2]/[CaSO4]2 c) Kc = [SO2]2[O2] d) Kc = [SO2][O2] e) Kc = 1/[SO2]2[O2] KEY 1)d 2)b 3)b 4)a 5)c 6)e 7)d 8)e 9)a 10)b 11)b 12)c 13)d 14)d 15)c 16)c 17)c 18)b 19)c