Equilibrium Constants and Reaction Rates in Chemistry, Exams of Chemistry

Download Equilibrium Constants and Reaction Rates in Chemistry and more Exams Chemistry in PDF only on Docsity! CHEM 1332 SUMMER 2005 TEST 2 VERSION 1 NO CHEATING! BUBBLE IN “1” IN THE P COLUMN TO GET YOUR GRADE POSTED!!!!! [the only way you’ll find out how you did!] 1. Which of the following statements is FALSE? (A) A reaction is at equilibrium when the forward and reverse reactions occur at the same rate. (B) At equilibrium, the concentrations of all species present are constant. (C) Even though a reaction at equilibrium appears to have stopped, reactions are still taking place. (D) The equilibrium position depends upon the quantity of the starting materials. (E) The equilibrium position depends upon the temperature of the reaction. 2. The gaseous reaction, 3 A + 6 B ∆ 3 C + 3 D has an equilibrium constant of 0.125. What is the value of the equilibrium constant for the reaction, C + D ∆ A + 2 B? (A) 0.00195 (B) 0.125 (C) 0.5 (D) 2 (E) 512 3. The reaction, NH4SH(s) ∆ NH3(g) + H2S(g) has an equilibrium constant, Kc, of 7 at 313 K. If a mixture consisting of 1.5 moles of NH4SH, 3.0 moles of NH3 and 3.0 moles of H2S in a 1 liter container is taken then: (A) The reaction is at equilibrium (B) The value of Q is 6 and the reaction goes to the right in order to reach equilibrium (C) The value of Q is 6 and the reaction goes to the left in order to reach equilibrium (D) The value of Q is 9 and the reaction goes to the left in order to reach equilibrium (E) The value of Q is 9 and the reaction goes to the right in order to reach equilibrium 4. For which of the following equilibria does Kp = Kc? (A) C(s) + CO2(g) ∆ 2 CO(g) (B) Cl2(g) ∆ 2 Cl(g) (C) 2 H2(g) + O2(g) ∆ 2 H2O(g) (D) CH4(g) + H2O(g) ∆ CO(g) + 3 H2(g) (E) N2(g) + O2(g) ∆ 2 NO(g) 1 5. At a given temperature, the equilibrium constant (Kc) for the reaction, 2 HCl(g) ∆ H2(g) + Cl2(g) is 12.5. When a given quantity of HCl is introduced into a 1.00 liter container, the equilibrium concentration of HCl is 1.25 moles/liter. What is the equilibrium concentration of H2(g)? (A) 4.42 moles/liter (B) 0.625 moles/liter (C) 0.3125 moles/liter (D) 0.2 moles/liter (E) 0.1 moles/liter 6. Starting with 0.0350 M COCl2, calculate the equilibrium constant (Kc) for the reaction, COCl2(g) ∆ CO(g) + Cl2(g), if the equilibrium concentration of CO is 0.0232 M. (A) 1.54 x 10-2 (B) 4.56 x 10-2 (C) 1.97 (D) 21.9 (E) 65.0 7. At 25.0 ºC, the reaction N2O4(g) ∆ 2 NO2(g) has an equilibrium constant, Kc, of 0.113. Calculate the concentration of NO2 at equilibrium when 2.5 moles of N2O4 are placed into a 1.00 liter container. (A) 0.532 moles/liter (B) 0.252 moles/liter (C) 0.504 moles/liter (D) 0.266 moles/liter (E) 0.956 moles/liter 8. The reaction, CaSO3(s) ∆ CaO(s) + SO2(g), has a ∆Hº value of -150 kJ at 250 ºC. Which of the following would reduce the amount of the poisonous gas, SO2, present at equilibrium. (A) Adding lots of CaO (B) Removing CaSO3 as it is formed (C) Performing the reaction in a large volume container (D) Performing the reaction at high temperatures (E) Adding an appropriate catalyst 9. Which of the following substances would NOT be considered to be amphiprotic in water? (A) H2O (B) HCO3- (C) NH3 (D) H2PO4- (E) HSO3- 10. The Kw of water at 90 ºC is 1.0 x 10-12. At this temperature: (A) Water is acidic because the [H3O+] in pure water is 1 x 10-6 and so the pH is 6 (B) 0.1 M HCl will have a pH of less than 1. (C) pH + pOH = 12 (D) The pH of 1 M NaOH would be 14 which is bigger than 12 so 1 M NaOH cannot exist at 90 ºC. 2 17. Which of the following solutions would be expected to have a pH of 7? (A) 0.1 M HCl (B) 0.25 M NaOH (C) 0.30 M NH4Br (D) 0.20 M NaF (E) 0.10 M NaCl 18. Identify the unknown particle X in each of the following: I. 8B → β+ + X II. 14C → X + 14N III. 238U → α + X (A) 8Be, β+, 234Th (B) 8Be, β+, 242Th (C) 8C, β−, 234Th (D) 8C, β−, 242Th (E) 8Be, β−, 234Th 19. The mass of carbon-14 is 14.003241 g/mol. Calculate the binding energy of a carbon-14 nucleus if the mass of a proton + electron is 1.00783 g/mol, the mass of a neutron = 1.00867 g/mol, the speed of light is 3.00 x 108 m/s and 1 J = 1 kg m2/s2. (A) 1.05 x 1016 J/mol (B) 1.02 x 1013 J/mol (C) 9.57 x 1012 J/mol (D) 1.69 x 1011 J/mol (E) 34 J/mol 20. The naturally occurring radioactive decay series that begins with 235U stops with formation of the stable 207Pb. The decay proceeds via a series of alpha and beta particle emissions. How many of each type of emission are involved in this series? (A) 5 α, 8 β (B) 14 α, 4 β (C) 7 α, 18 β (D) 7 α, 4 β (E) 7 α, 8 β 5 CHEM 1332 SUMMER 2005 TEST 2 VERSION 2 NO CHEATING! BUBBLE IN “1” IN THE P COLUMN TO GET YOUR GRADE POSTED!!!!! [the only way you’ll find out how you did!] 1. Starting with 0.0350 M COCl2, calculate the equilibrium constant (Kc) for the reaction, COCl2(g) ∆ CO(g) + Cl2(g), if the equilibrium concentration of CO is 0.0232 M. (A) 1.54 x 10-2 (B) 4.56 x 10-2 (C) 1.97 (D) 21.9 (E) 65.0 2. At 25.0 ºC, the reaction N2O4(g) ∆ 2 NO2(g) has an equilibrium constant, Kc, of 0.113. Calculate the concentration of NO2 at equilibrium when 2.5 moles of N2O4 are placed into a 1.00 liter container. (A) 0.532 moles/liter (B) 0.252 moles/liter (C) 0.504 moles/liter (D) 0.266 moles/liter (E) 0.956 moles/liter 3. The reaction, CaSO3(s) ∆ CaO(s) + SO2(g), has a ∆Hº value of -150 kJ at 250 ºC. Which of the following would reduce the amount of the poisonous gas, SO2, present at equilibrium. (A) Adding lots of CaO (B) Removing CaSO3 as it is formed (C) Performing the reaction in a large volume container (D) Performing the reaction at high temperatures (E) Adding an appropriate catalyst 4. Which of the following substances would NOT be considered to be amphiprotic in water? (A) H2O (B) HCO3- (C) NH3 (D) H2PO4- (E) HSO3- 5. The Kw of water at 90 ºC is 1.0 x 10-12. At this temperature: (A) Water is acidic because the [H3O+] in pure water is 1 x 10-6 and so the pH is 6 (B) 0.1 M HCl will have a pH of less than 1. (C) pH + pOH = 12 (D) The pH of 1 M NaOH would be 14 which is bigger than 12 so 1 M NaOH cannot exist at 90 ºC. (E) None of these are correct. 1 2