CHEM 102 Spring 14 Exam 3(A) Questions and Answers,100% CORRECT

CHEM 102 Spring 14 Exam 3(A) Questions and Answers Potentially useful: 1. Please choose letter “a” as your answer for this question. 2. A weak acid is 5% ionized at equilibrium. Therefore we can say that the ionization reaction is -favored, because . a. product; the amount of products the amount of reactants b. reactant; the amount of products the amount of reactants c. reactant; the amount of products the amount of reactants d. product; the amount of products the amount of reactants e. neither; not enough information is available to reach a conclusion 3. Which of the following statements is/are correct? I. The addition of a catalyst increases the equilibrium constant for a chemical reaction. II. Equilibrium is established when the rates of the forward and backward reactions are equal. III. The value of the equilibrium constant for a reaction is dependent on the temperature of the chemical system. a. I only b. II only c. III only d. II and III e. I, II and III 4. Consider the reaction H2O(g) + C(s) CO(g) + H2(g) Consider an equilibrium mixture of these substances. If the pressure is increased by compressing the mixture, equilibrium will ; if pressure is increased by adding an inert gas to the mixture, equilibrium will . a. shift to the left; shift to the left b. shift to the right; shift to the left c. shift to the left; remain unchanged d. shift to the right; remain unchanged e. shift to the right; shift to the right 5. If the value of Kc for a given reaction at a constant temperature is a large number, the energy of the products is likely to be the energy of the reactants because . a. greater than; the value of Kc favors the reactants b. less than; the value of Kc favors the reactants c. the same as; the value of Kc favors neither the products nor the reactants d. greater than; the value of Kc favors the products e. less than; the value of Kc favors the products 6. Consider the endothermic reaction, which is in an open system (so ignore changes in volume and pressure) C(s) + CO2(g) 2CO(g) If such a system at equilibrium is heated, equilibrium will , because . a. be unchanged; temperature has no effect on equilibrium b. shift to the left; increased temperature favors an exothermic reaction c. shift to the right; increased temperature favors an exothermic reaction d. shift to the right; increased temperature favors an endothermic reaction e. shift to the left; increased temperature favors an endothermic reaction 7. For the reaction ethanol + acetic acid ethyl acetate Kc = 0.95. A mixture of the three substances contains 0.45 M ethanol, 0.45 M acetic acid and 1.1 M ethyl acetate. Which statement is true? a. Q K, so the system will react left to right. b. Q K, so the system will react right to left. c. The mixture is at equilibrium. d. Q K, so the system will react left to right. e. Q K, so the system will react right to left. 8. For the reaction 2A 3B Kc = 1.37. If the concentrations of A and B are equal, what is the value of that concentration? a. 0.685 M b. 0.822 M c. 1.17 M d. 1.37 M e. 1.88 m 9. The value of Kc for the reaction A B is 1.4 × 1015. At equilibrium: a. The amount of A is slightly less than the amount of B. b. The amount of A is much larger than the amount of B. c. The amount of A is much less than the amount of B. d. The amount of A is very close to the amount of B. e. More information is needed to make any statement about the relative amounts of A and B. 10. Consider the reaction COCl2(g) CO(g) + Cl2(g) At equilibrium, [CO] = 4.14 × 10-6 M; [Cl2] = 4.14 × 10-6 M; and [COCl2] = 0.0627 M. Calculate the value of the equilibrium constant, Kc. a. 2.73 × 10-10 b. 6.60 × 10-5 c. 1.32 × 10-4 d. 1.51 × 104 e. 3.66 × 109 11. Consider the reaction Br2(g) + Cl2(g) 2BrCl(g) If the partial pressures in an equilibrium mixture of Br2, Cl2, and BrCl are 1.12 atm, 1.26 atm, and 3.14 atm, respectively, the value of Kp for this reaction at this temperature is a. 7.0. b. 4.7. c. 1.9. d. 0.53. e. 0.14. 12. What is the equilibrium constant expression for the reaction given below? 4 NH3(g) + 5 O2(g) 4 NO(g) + 6 H2O(g) a. b. c. d. e. 13. If the equilibrium constants for the two reactions 2 HCl(g) H2(g) + Cl2(g) and I2(g) + Cl2(g) 2 ICl(g) are denoted K1 and K2 respectively, then the equilibrium constant for the reaction 2 HCl(g) + I2(g) 2 ICl(g) + H2(g) equals a. (K1/K2)2. b. (K1K2)2. c. K1K2. d. K1+K2. e. K1K2/2. 14. When a solution is supersaturated the concentration of the solute is the solubility, and solute will dissolve. a. less than; more b. equal to; no more c. greater than; more d. less than; no more e. greater than; no more 15. The process of dissolving is favored if the interactions are weaker than the interactions. a. solute-solvent; solute-solute and solvent-solvent b. solvent-solvent; solute-solute and solute-solvent c. solute-solute and solvent-solvent; solute-solvent d. solute-solvent and solvent-solvent; solute-solute e. solute-solute; solute-solvent and solvent-solvent 16. In the following chemical reaction, HF(aq) + H2O(l) F-(aq) + H3O+(aq) a. HF is an acid and H3O+ is its conjugate base. b. HF is a base and H3O+ is its conjugate acid. c. H2O is an acid and F- is its conjugate base. d. H2O is a base and H3O+ is its conjugate acid. e. HF is an acid and H2O is its conjugate base. 17. One water molecule can donate a proton to another in a process called ; the equilibrium constant expression for this reaction is . a. neutralization; b. autoionization; c. protonation; d. hydrolysis; e. autoionization; [H3O+][OH-] 18. In a 1.2 M solution of KOH, a strong base, [H3O+] = , and [OH-] = . a. 1.0 × 10-7 M; 1.0 × 10-7 M b. 8.3 × 10-15 M; 1.0 × 10-14 M c. 8.3 × 10-15 M; 1.2 M d. 1.2 M; 8.3 × 10-15 M e. 1.2 M; 1.2 M 19. Which of the following is the correct reaction of methylamine (CH3NH2) and water? a. CH3NH2(aq) + H2O(l) CH3NH-(aq) + H3O+(aq) b. CH3NH2(aq) + H2O(l) CH3NH +(aq) + OH-(aq) c. CH3NH2(aq) + H2O(l) CH3NH +(aq) + H3O+(aq) d. CH3NH2(aq) + H2O(l) CH3OH(aq) + NH3(aq) e. CH3NH2(aq) + H2O(l) CH3NH-(aq) + OH-(aq) 20. Calculate the pH of a solution where [OH-] = 4.6 × 10-4. Is this solution acidic or basic? a. 3.34; acidic b. 3.34; basic c. 9.40; basic d. 10.66; acidic e. 10.66; basic 21. The larger the value of Ka a. the less highly dissociated the acid and the weaker the acid. b. the less highly dissociated the acid and the stronger the acid. c. the more highly dissociated the acid and the weaker the acid. d. the more highly dissociated the acid and the stronger the acid. e. none of these choices are correct 22. For the dissociation of a very weak acid, HA, in water a. Ka = [HA][H3O+][ A-] b. Ka = [H3O+][ A-] c. Ka = [H3O+][ A-] / [H2O] d. Ka = [HA] / [A-][H3O+] e. Ka = [H3O+][ A-] / [HA] 23. In a neutral polyprotic acid, the value of Ka2 will be the value of Ka1 because . a. smaller than; it is more difficult to remove a hydrogen ion from a cation than from a neutral molecule b. larger than; it is more difficult to remove a hydrogen ion from an anion than from a neutral molecule c. larger than; it is more difficult to remove a hydrogen ion from a cation than from a neutral molecule d. smaller than; it is more difficult to remove a hydrogen ion from an anion than from a neutral molecule e. the same as; both hydrogen ions are bonded to the same anion 24. The pH of a 0.50 M solution of the weak acid HA is 4.76. The value of Ka is . a. 6.0 × 10-10 b. 1.7 × 10-5 c. 3.5 × 10-5 d. 7.6 × 10-4 e. 9.24 25. The amino acid alanine has a neutral side-chain with no acid-base properties. At pH = 7, it will be a a. singly charged anion. b. doubly charged anion. c. cation. d. zwitterion. e. neutral molecule with no charged groups. 26. The poison strychnine is a weakly basic compound with Kb = 1.8 × 10-6. What is the pH of a 0.058 M solution of strychnine? a. 3.49 b. 7.30 c. 8.26 d 10.51 . e 12.76 . 27. Which of the following was mentioned in lecture? (extra 4 points) a. Acid/base chemistry of the Martian soil. b. Applications of Le Chatelier’s principle to the prediction of volcanic eruptions. c. An earthquake once caused the Mississippi River to run backwards. d. The concept of Q in drug design. e. All of the above.