CHE 102: Final Exam Review

1 CHE 102 Final Exam Student’s Name: Student’s No.: Instructor: Serial No.: Section: 1 2 3 4 5 6 7 8 9 10 11 12 13 16 17 18 19 20 21 22 23 24 25 26 27 28 14 15 * Each of the question bellow is followed by four suggested answers. Select the one that is best in each case and type it in the above table. 1. The pH of a 1 x 10-10 M HCl(aq) is approximately equal to --------. B. 4.0 C. 7.0 A. 10.0 D. 5.0 Consider the following ionization constants of some weak acids for the next 2 questions: Ka Acid CH3COOH 1.8 x 10-5 HF 7.1 x 10-4 HCN 4.9 x 10-10 HNO2 4.5 x 10-4 + NH4 5.6 x 10-10 2. Which of the following is the strongest base? A. NH3 B. F 3. Predict the direction of the following reaction in aqueous solution C. CH3COO- D. CN HNO2(aq) + CN(aq) ⇌ HCN(aq) + NO2(aq) A. The net reaction will shifted to the left favoring HNO2 and CN B. In the middle C. The net reaction will shifted to the right favoring HCN and NO2 D. Can not be determined 4. What is the original molarity (initial concentration) of a solution of a monoprotic acid (HA) whose pH is 2.44 at equilibrium? (Ka HA = 2.64 x 10-4) C. 20 M D. 0.10 M A. 13.8 M B. 0.05 M 5. The Kw for water at 0ºC is 1.6 x 10-15. What is the pH and pOH of water at 0ºC? A. pH = pOH = 7.0 B. pH = 6.6, pOH = 7.4 C. pH = pOH = 7.4 D. pH = 7.4, pOH = 6.6 6. Which one of the following solutions would be expected to have the highest % ionization? A. 0.1 M HF B. 0.05 M HF C. 1.0 M HF D. 5.0 M HF 7. At 25ºC what is the pH of a 1.75 M solution of NaCN? (Ka HCN = 4.9 x 10-10) A. 11.78 B. 10.88 C. 3.44 D. 1.18 2 8. 9. Water can not function as which one of the following? A. a Bronsted acid B. a Bronsted Base C. a Lewis acid D. a Lewis base Which one of the following compounds is the strongest acid? A. HClO3 B. HClO2 C. HClO D. HClO4 10. An aqueous solution of NaHSO3 will be _____. (Ka1 = 1.7 x 10-2, Ka2 = 6.4 x 10-8) C. Basic D. non A. neutral B. acidic 11. H3PO4 has the following ionization constants: Ka1 = 7.5 x 10-3, Ka2 = 6.2 x 10-8, Ka3 = 4.8 x 10-13. To make up a buffer solution of pH 7.21. Which of the following combination would you choose? B. H3PO4/H2PO4─ C. HPO4─2/PO4─3 D. H3PO4/KOH A. H2PO4─/ HPO4─2 12. Calculate the pH of 1.0 L of the buffer 0.30 M CH3CO2H/0.36 M CH3CO2Na after the addition of 0.1 mole of HCl? ( Ka for CH3CO2H = 1.8 x 10-5) Assume that the volume of the solution does not change when the HCl is added. A. 4.82 B. 4.38 C. 5.11 D. 4.56 13. Addition NH4Cl, to a NH3 solution_____. A. increases the pH of the solution C. increases the concentration of OH- B. decreases the pH of the solution D. has no effect on the pH of the solution 14. Which of the following statements is correct? A. At equilibrium the reaction is completely stopped B. At equilibrium the rate constant for the forward reaction equals that of the reverse reaction C. At equilibrium there are equal amounts of reactants and products D. At equilibrium the forward and the reverse reactions are occurring at the same rate 15. Consider the following reaction at equilibrium: A(g) ⇌ 2 B(g). Based on the following data, which of the following is correct? Temperature (ºC) [A] [B] 200 0.0125 0.843 300 0.171 0.764 400 0.250 0.724 A. the reaction is exothermic. B. the reaction is endothermic. C. Kc at 200ºC > Kc at 300ºC. D. Kp = Kc 16. At 430ºC, the equilibrium constant (Kc) for the reaction: H2 + I2 ⇌ 2 HI is 64. If you start with [H2] = 0.08 M, [I2] = 0.08 M and [HI] = 0.64 M, what are the concentrations of HI, H2, and I2 at equilibrium? [H2] = 0.08 M [I2] = 0.08 M [HI] = 0.64 M A. B. [H2] = 0.04 M [I2] = 0.04 M [HI] = 0.32 M C. [H2] = 0.32 M [I2] = 0.32 M [HI] = 0.24 M D. [H2] = 0.015 M [I2] = 0.015 M [HI] = 0.12 M 17. For the reaction: 2 A(g) + 3 B2(g) ⇌ 2 AB3(g) An increase in pressure would ---------. A. increase the value of the equilibrium constant, Kc B. shift the reaction to form more reactants (from Right to Left) C. shift the reaction to form more products (from Left to Right) D. no affect equilibrium 3 18. The standard free energy change for the dissociation of silver chromate is +66.2 kJ/ mol at 25oC. Ag2CrO4(s) ⇌ 2 Ag+(aq) + CrO42-(aq) What is the [Ag ] ions in the solution if the [CrO42-] ions at the equilibrium is 2.0 × 10-3 M? B. 6.2 × 10-7 M C. 3.5 × 10-5 M D. 3.5 × 10-4 M A. 1.2 × 10-9 M + 19. Consider the equilibrium AB2(aq) ⇌ A(aq) + 2 B(aq) Suppose you start with 0.2 M of AB2 in a 1.0 L flask at 500 K. Calculate Kc for the equilibrium at the same temperature if the equilibrium concentration of B is 0.1 M. A. 1.0 x 10-2 B. 3.33 x 10-3 C. 5.0 x 10-4 D. 2.5 x 10-3 20. Which of the following will be present in the smallest concentration in an aqueous 0.025 M H2CO3 solution? (Ka1 = 4.3 x 10-7, Ka2 = 5.6 x 10-11) A. H2CO3 B. H3O+ C. HCO3– D. CO32– 21. The incorrect statement about the catalyst effect is ------. A. increases the rate of reaction B. changes the mechanism of the reaction C. lowers the activation energy D. increases the value of the equilibrium constant 22. The molarity of pure water is -----------. ( water density is 1.0 g/ml) A.5.55 M B. 55.5 M C. 1000 M D. 1.0 M 23. Calculate the boiling point of an aqueous solution of a nonvolatile solute that freezes at – 3.4 oC. (for H2O :Kb = 0.52 oC/m, Kf = 1.86 oC/m) A. 100 .95 oC B. 100 .84 oC C. 100.52 oC D. 100.31 oC 24. Which of the species below exhibits hydrogen bonding? A. CH3-S-CH3 B. CH3OCH3 C. CH3OH D. CH3SH 25. The three Laws of the thermodynamics are as follows: I. The total ------- of the universe is constant. II. The total --------- of the universe increases for a spontaneouse process. III. The ---------- of a perfectly ordered crystal at 0 K is 0. The answers in order are -----------. A. energy, energy, energy B. energy, entropy, energy D. entropy, energy, entropy C. energy, entropy, entropy 26. Calculate ΔGº for the following reaction, N2(g) + 3 H2O(l)  2 NH3(g) + 3/2 O2(g) given that ΔGºf[H2O(l)] = −237.1 kJ/mol and ΔGºf [NH3(g)] = −16.5 kJ/mol. C. -221 kJ A. 221 kJ B. 678 kJ D. 348 kJ 27. Use the information below to determine the value of the rate constant for the following reaction: A + B  P Experiment [A], M [B], M Rate, M/s 1 0.273 0.763 2.83 2 0.273 1.526 2.83 3 0.819 0.763 25.47 A. 38.0 B. 0.278 C. 13.2 D. 42.0 28. Consider the following reaction at 25°C: C(s) + H2O(g)  CO(g) + H2(g) If ΔGº = 91.2 KJand ΔSº = 135 J/K, what is the value of ΔHº for this reaction at 25°C? A. 40.3 kJ B. 226 kJ C. 91.3 kJ D. 131.4 kJ