1 Practice exam III (100 points) + EC (8 points) CHM 1210, Department of Chemistry Some potentially useful equations and relationships, which will be provided to you during exam. 1 inch = 2.54 cm 12 inches = 1 ft 1 mile = 1.6093 km 1 gal = 3.7854 L 1 pound = 453.59 g 1 kg = 2.2046 pound 1 amu = 1.6605 x 10-24 g π = 3.14159 e- = 1.602 177  10–19 C e/m of the electron = 1.758 819  108 C/g for an electron m = 1.672 623  10–24 g for a proton and m = 1.674 927  10–24 g for a neutron Avogadro’s number: NA = 6.022 x 1023 formula units PART I. Multiple Choice Questions, 40 Points (10 questions x 4 points/each question) 1. What is the concentration of FeCl3 in a solution prepared by dissolving 10.0 g of FeCl3 in enough water to make 0.275 L of solution? A) 2.24 × 10-4 M B) 0.224 M C) 4.46 M D) 4.46 × 103 M E) 4.46 × 10-3 M 2. How many milliliters of a 9.0 M H2SO4 solution are needed to make 0.25 L of a 3.5 M H2SO4 solution? A) 0.097 mL B) 0.64 mL C) 9.7 mL D) 640 mL E) 97 mL 3. When 10.0 g of calcium metal is reacted with water, 5.00 g of calcium hydroxide is produced. Using the following balanced equation, calculate the percent yield for the reaction? Ca(s) + 2 H2O(l) → Ca(OH)2(aq) + H2(g) A) 13.5% B) 27.1% C) 50.0% D) 92.4% E) 100% 4. Which of the following choices represents the net ionic equation for the reaction of sulfurous acid with sodium hydroxide? A) H2SO3 (aq) + 2 NaOH(aq)  2 H2O(l) + Na2SO3(aq) B) 2 H+(aq) + SO32-(aq) + 2 Na+(aq) + 2 OH-(aq)  2 Na+(aq) + SO32-(aq) + 2 H2O(l) C) H2SO3 (aq) + 2 OH- (aq)  2 H2O(l) + SO32-(aq) D) H+(aq) + OH-(aq)  H2O(l) E) none of the above 5. Identify the spectator ions in the reaction of lead (II) nitrate with potassium iodide. A) Pb2+(aq) and I-(aq) B) K+(aq) and NO3-(aq) C) Pb2+(aq) and NO3-(aq) D) K+(aq) and I-(aq) E) K+(aq) only2 6. Choose the correct oxidation number for vanadium in the V2O74- ion. A) +2 B) +3 C) +4 D) +5 E) +6 7. Using the following portion of the activity series for oxidation half reactions Ca(s) → Ca2+(aq) + 2e- Mg(s) → Mg2+(aq) + 2e- Zn(s) → Zn2+(aq) + 2e- Cu(s) → Cu2+(aq) + 2e- determine which reaction will not occur A) Ca(s) with Cu2+(aq) B) Ca(s) with Zn2+(aq) C) Ca(s) with Mg2+(aq) D) Zn(s) with Mg2+(aq) E) Zn(s) with Cu2+(aq) 8. Which species functions as the oxidizing agent in the following reduction-oxidation reaction: ).(2Zn)Cu()(2Cu)Zn( aqsaqs A) Cu(s) B) Cu2+(aq) C) Zn(s) D) Zn2+(aq) E) none of the above 9. What is the molar concentration of sodium ions in a 0.350 M Na3PO4 solution? A) 0.117 M B) 0.350 M C) 1.05 M D) 1.40 M E) 1.450 M 10. How many milliliters of 0.260 M Na2S are needed to react with 25.00 mL of 0.315 M AgNO3? Na2S(aq) + 2 AgNO3(aq) → 2 NaNO3(aq) + Ag2S(s) A) 15.1 mL B) 30.3 mL C) 41.3 mL D) 60.6 mL E) 90.9 mL End of Multiple Choice Questions3 PART II. Problem Solving, 60 Points Start the response to each question on this page, immediately after the text problem. Show clearly how you arrive at your conclusions. No credit awarded for unsupported answers! Express your final answers in the box with the correct number of significant figures in an unambiguous manner. 11. (17 points) Lithium oxide is used aboard the space shuttle to remove water from the air supply according to the following balanced equation: Li2O(s) + H2O(g) → 2LiOH(s) a) If 80.0 g of water are to be removed and 65.0 g of Li2O are available, which reactant is limiting? Show all calculations in support of your answer. (10 points) b) How many grams of excess reactant remain? (3 points) c) How many grams of LiOH are produced? (4 points) Limiting reactant = ________ Mass of excess reactant remaining = g _________ Mass of LiOH = _______ g4 12. (10 points) A compound was found to contain 38.7% C, 9.7% H, and 51.6% O. An experiment determined that the compound had a molecular weight of 62.0 g/mol. a) What is its empirical formula? (7 points) b) What is its molecular formula? (3 points) Empirical formula: Molecular formula:5 13. (33 points) a) Identify each of the following aqueous reactions as a precipitation (PPTN) reaction, an acid-base (A-B) reaction, or an oxidation-reduction (REDOX) reaction. Write the corresponding abbreviations (i.e., PPTN, A-B, or REDOX) in the spaces provided to the right of each reaction. (5 points) Pb(NO3)2 (aq) + 2 KI (aq) → 2 KNO3 (aq) + PbI2 (s) _____ CH3CO2H (aq) + KOH (aq) → H2O (l) + CH3CO2K (aq) _____ H2SO4 (aq) + 2 AgNO3 (aq) → Ag2SO4 (s) + 2 HNO3 (aq) _____ HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l) _____ 2 HCl (aq) + Mg (s) → H2 (g) + MgCl2 (aq) _____ b) Indicate wheter the following compounds are soluble or insoluble in water. Do not list the solubility rules!. Simply write YES for a soluble compound and NOT for an insoluble compound in the spaces provided to the right of each compound. (10 points) AgC2H3O2 _____ Al2O3 _____ Ca(NO3)2 _____ CaCO3 _____ FeS _____ BaCl2 _____ ZnO _____ Na2S _____ CoCl2 _____ Hg2SO4 _____ c) Indicate whether the following chemical compounds are strong electrolytes (SE), weak electrolytes (WE), or nonelectrolytes (NE). Additionally identify the chemical compounds as strong acids (SA), weak acids (WA), strong bases (SB) or weak bases (WB) - leave blank if none of these applies. (10 points). Compound Weak electrolyte (WE) Strong electrolyte (SE) Nonelectrolyte (NE) Weak Acid (WA) or Strong Acid (SA) Strong Base (SB) or Weak Base (WB) HCl _______________ ____________________________________ NaOH _______________ ____________________________________ NH3 _______________ ____________________________________ H2O _______________ ____________________________________ H3PO4 _______________ ____________________________________6 d) Balance the following oxidation-reduction equation in basic medium. Specify the method used for balancing each redox reaction in the space provided. Show clearly your work (i.e., each step of the method)! (8 points) MnO4- (aq) + SO32- (aq) → MnO42- (aq) + SO42- (aq) Method: