FinalExam sample problems_081711

FinalExam sample problems_081711 - CONCEPTS. 3 pts each 1....

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Unformatted text preview: CONCEPTS. 3 pts each 1. Which of the following compounds will produce a basic aqueous solution at 25C? A) NH4Cl B) NaCl C) NaF D) all of these E) none of the above Which of the following aqueous solutions will have the smallest percent ionization at 25C if the Ka of formic acid is 1.81 x 10-4 and the Ka of lactic acid is 1.38 x 10-4? A) 0.100 M lactic acid B) 0.200 M lactic acid C) 0.100 M formic acid D) 0.200 M formic acid E) This cannot be predicted from the given information. Which of the following solutions will have the highest pH? A) 0.10 M NH3 (Kb = 1.8 x 105) B) 0.10 M HOCl (Ka = 2.9 x 108) C) 0.10 M CH3NH2 (Kb = 4.2 x 104) D) 0.10 M HIO3 (Ka = 1.6 x 101) Which of the following solutions will be the best conductor of electrical current? A) methyl alcohol, CH3OH (aq) B) glucose, C6H12O6 (aq) C) potassium chloride, KCl (aq) D) bromine, Br2 (aq) E) not enough information is provided 2. 3. 4. 5. 6. For a neutral solution, it must be true that __________. An aqueous solution of silver nitrate is added to an aqueous solution of potassium chromate, and this reaction produces a solid. What is the formula for the solid? For Mg(OH)2 (s), Ksp = 1.2 x 10-11. As the pH is raised, the solubility of Mg(OH)2 in water should __________. Methyl orange is an indicator with a Ka of 1 104. Its acid form, HIn, is red, while its base form, In, is yellow. At pH 6.0, the indicator will be _________. Addition of NH4Cl to an aqueous solution of NH3 will cause _______________. 7. 8. 9. 10. Arranging the following solutions, 0.20 M HF (Ka = 7.2 x 104), 0.20 M HOBr (Ka = 2.5 x 109), 0.20 M HClO2 (Ka = 1.1 x 102), in order of increasing pH would give _______________. 11. In comparing the three ionization constants for citric acid, H3C6H7O7, one would expect __________________. 12. How would you make the best buffer at a pH of 4.74 using one or both of the following acids/bases? (Ka for HC2H3O2 is 1.8 x 10-5; Kb for NH3 is 1.8 x 10-5) 13. Hydroxylamine, HONH2, has a Kb of X. The Ka for HONH3+ would therefore be __________ (in terms of X). SHORT CALCULATION. 5 pts each 1. A mixture of HBrO (Ka = 2.5 x 109) and NaBrO (Kb = 4.0 x 106) would function best as a buffer at a pH of ________________. Calculate the pH of a 0.1 M NaCN solution (Ka for HCN = 4.9 x 10-10). When the equation Zn + As2O3 AsH3 + Zn2+ (acidic solution) is balanced using the smallest whole-number coefficients, what is the coefficient of H+? A mixture of 82.49 g of aluminum and 117.65 g of oxygen is allowed to react. Identify the limiting reactant and determine the mass of the excess reactant present in the vessel when the reaction is complete. 4 Al (s) + 3 O2 (aq) 2 Al2O3 (s) 5. At a certain temperature, K for the reaction 2NO2 ! N2O4 -1 is 7.5 M . If 2.0 mol of NO2 is placed in a 2.0-liter container and permitted to react at this temperature, calculate the concentration of N2O4 at equilibrium. Consider the weak base hydroxylamine (HONH2), for which the Kb = 1.1 x 108 at 25C. If 100.0 mL of a 0.500 M aqueous hydroxylamine solution is mixed with 100.0 mL of 0.500 M aqueous hydrochloric acid at 25C, the resulting solution will have pH Copper(II) oxalate is only slightly soluble in water, having Ksp = 2.9 x 10-8 at 25C. This means that the solubility of CuC2O4 in water at 25C is. What volume of 0.235 M NaOH must be added to 60.00 mL of 0.200 M acetic acid (Ka = 1.76 x 10-5) to give a solution having a pH of 4.65? A monoprotic weak acid, when dissolved in water, is 0.92% dissociated and produces a solution with pH = 3.42. Calculate Ka for the acid. 2. 3. 4. 6. 7. 8. 9. 10. Calculate the pH of a solution prepared by mixing 50 mL of a 0.10 M solution of HF with 25 mL of a 0.20 M solution of NaF. pKa is 3.14. 11. You have solutions of 0.200 M HNO2 and 0.200 M KNO2 with which to prepare a buffer that has a pH of 3.000. What volumes of HNO2 and KNO2 are required to make 1 L of buffered solution? (Ka for HNO2 = 4.00 x 10-4) 12. A 50.00-mL sample of 0.100 M KOH is titrated with 0.100 M HNO3. Calculate the pH of the solution after 52.00 mL of HNO3 is added. 13. The solubility of Cd(OH)2 in water is 1.7 105 mol/L at 25C. What is Ksp for Cd(OH)2? 14. Calculate the pH of a solution made by mixing equal volumes of a solution of HCl with a pH of 1.44 and a solution of HNO3 with a pH of 2.74. (Assume the volumes are additive.) 15. If 30 mL of 5.0 104 M Ca(NO3)2 is added to 70 mL of 2.0 104 M NaF, will a precipitate form? (Ksp of CaF2 = 4.0 1011) 16. The mass percent of iron in an iron oxide is 77.7%. Find the empirical formula. 17. A 34.00 mL sample of 0.0291 M Ca(OH)2 required 24.75 mL of aqueous HCl for neutralization according to the reaction below. What is the concentration of the HCl Ca(OH)2 (aq) + 2 HCl (aq) ! CaCl2 (aq) + H2O (l) 18. The density of a certain diatomic gas is 1.696 g/L at STP. Identify the gas. 19. Calculate the mass in grams of 3.65 x 1020 molecules of SO3. ...
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This note was uploaded on 01/19/2012 for the course CHEM 142A taught by Professor Campbell during the Summer '11 term at University of Washington.

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