1 Practice exam II (100 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 PART I. Multiple Choice Questions, 42 Points (12 questions x 3.5 points/each question) 1. Apple juice is an example of A) a compound B) an element C) a heterogenous mixture D) a homogenous mixture E) pure substance 2. Use the periodic table below to answer the following question. Which elements commonly form anions? A) A and B B) A and C C) B and D D) C and D E) A, B, C, and D 3. How many H+ ions can the acid, H2CO3, donate per molecule? A) 0 B) 1 C) 2 D) 3 E) 4 4. When dissolved in water, KOH behaves as A) an acid that forms K+ and OH- ions. B) an acid that forms KO- and H+ ions C) a base that forms K+ and OH- ions. D) a base that forms KO- and H+ ions E) none of the above. 5. The definitive distinction between ionic bonding and covalent bonding is that A) ionic bonding involves a sharing of electrons and covalent bonding involves a transfer of electrons. B) ionic bonding involves a transfer of electrons and covalent bonding involves a sharing of electrons. C) ionic bonding requires two nonmetals and covalent bonding requires a metal and a nonmetal. D) covalent bonding requires two metals and ionic bonding requires a metal and a nonmetal. E) none of the above.2 6. Which of the following contains both ionic and covalent bonds? A) CaI2 B) CO C) CaSO4 D) SF6 E) H2 7. Give the molecular formula corresponding to the following ball-and-stick molecular representation of naphthalene (gray = C, unshaded = H). In writing the formula, list the atoms in alphabetical order. A) CH B) C5H4 C) C8H10 D) C10H8 E) C10H10 8. How many silver atoms are contained in 3.75 moles of silver? A) 6.23 × 1024 silver atoms B) 2.26 × 1024 silver atoms C) 1.61 × 1023 silver atoms D) 2.44 × 1026 silver atoms E) 6.50 × 1025 silver atoms 9. Calculate the mass (in g) of 1.9 x 1024 atoms of Pb. A) 3.9 × 102 g B) 2.4 × 102 g C) 3.2 × 102 g D) 1.5 × 102 g E) 6.5 × 102 g 10. 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 11. 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 12. 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% End of Multiple Choice Questions3 PART II. Problem Solving, 58 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. 13. PRINT the missing name or the missing formula for the following chemical compounds and indicate whether binary compounds are ionic or covalent (circle one answer). Correct spelling of words and correct representation of chemical elements is required for full credit. (24 points) nitric acid HClO4 potassium hydroxide HCl(aq) ammonium sulfate LiHCO3 N2O4 ( ionic / covalent ) copper (II) oxide ( ionic / covalent ) phosphorous trichloride ( ionic / covalent ) V2O3 ( ionic / covalent )4 14. Balance the following equations (12 points) a) SiCl4 + H2O SiO2 + HCl b) NO2 + H2O HNO3 + NO5 15. (22 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? (4 points) c) How many grams of LiOH are produced? (8 points) Limiting reactant = ________ Mass of excess reactant remaining = g _________ Mass of LiOH = _______ g6 Extra Credit Questions – 6 points Only attempt if you have completed the rest of the test 16. How does the image obtained by a scanning tunneling microscope differ from that obtained by the usual optical microscope? (6
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