CHEM Exam 1 Sept. 20, 2018

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1 HEM Exam 1 Sept. 20, 2018 onstants and onversion Factors Avogadro's Number: NA = 6.02x10 23 mol -1 onversion Factors: 1 lb = 454 g 1 ft = 12 in 1 in = 2.54 cm 1 ton = 2,000 lb 1 week = 7 days Molar Masses: O P S K = 39.1 As H8O3-92. Al2O P4O Bi2O3-466.

2 HEM Exam 1 Sept. 20, 2017 (76) MULTIPLE HOIE (4 points per question) (ircle the ONE correct answer) Name NOTE: Required Molar Masses and non-metric conversion factors are given on the cover sheet. 1. The density of opper is 8.92 g/cm 3. What is the approximate mass, in tons, of a cubic block of copper that has a length of 12.0 m (meters) on each side? (A) 1.7x10 4 tons () 1.2x10-2 tons (B) 5.4x10 9 tons (D) 3.4x10 2 tons 2. onsider a bacterial cell of dimensions 1.2 m x 1.2 m x 4.0 m. Approximately how many of these cells will occupy a volume of 15. cm 3? (A) 2.6x10 12 cells (B) 5,8x10 6 cells () 2.6.x10 6 cells (D) None of the above 3. A 210 Po 2- ion on contains how many neutrons (n) and electrons (e)? (A) 84 n & 86 e () 126 n & 82 e (B) 210 n & 86 e (D) 126 n & 86 e 4. An ion containing 34 protons, 36 electrons and 44 neutrons has the atomic symbol: (A) 78 Kr 2- (B) 78 Se 2- () 80 Se 2- (D) 78 Ge 2-5. In a Mass Spectrometer, after positive ions are created by a high energy electron beam, charged plates are used to accelerate and focus the ions. The ions are then deflected by a field, and ions are deflected by a greater amount. (A) electric, heavier () magnetic, lighter (B) electric, lighter (D) magnetic, heavier 6. The half-life for the nuclear transformation of 40 K to 40 Ar is 1.25 billion years. If a rock was formed 2.2 billion years ago, then the ratio of the two elements, [ 40 K]/[ 40 Ar], is approximately: (A) 2.3 (B) 0.25 () 0.42 (D) 1.35

3 7. Phosphorus-32 is a commonly used radioisotope in biochemical research, particularly in the study of nucleic acids. The first order rate constant for the decay of 32 P is k = day -1. If one starts with 250. mg Na3 32 PO4 approximately how many mg of Na3 32 PO4 remain after 3.0 weeks? (A) 90. mg (B) 62 mg () 24. mg (D) 220. mg 8. Hypothetical element, Saffium (Sf), contains two naturally occurring isotopes, 158 Sf and 164 Sf. The average atomic weight of Sf is amu. What is the approximate natural abundance of 164 Sf in this element? (A) 0.30% (B) 35% () 60% (D) 65% 9. What is the name of the covalent compound, As2Se5? (A) diarsenic pentaselenate () diarsenic pentaselenide (B) arsenic selenide (D) arsenic(ii) pentaselenide 10. The formula of the ionic compound, iron(ii) sulfite, is (A) Fe2(SO3)3 (B) Fe3(SO3)2 () FeSO3 (D) Fe2(SO4)3 11. Which ionic formula is incorrect? (A) a2o3 (B) KNO2 () Sr(N)2 (D) (NH4)2SO4 12. The name of the compound with the structure on the right is: (A) 4-propylhexane (B) 3,3,3-trimethylhexane () 4-ethylheptane (D) 3-propylhexane 13. The name of the compound with the condensed structural formula, H3BrHHH2, is: (A) 2-bromo-2,4-pentadiyne () 2-bromo-2,4-pentadiene (B) 4-bromo-1,3-pentadiene () 4-bromopenta-2-ene,4-yne 14. The name of the compound with the condensed structural formula, HF2H2H, is: (A) 6-difluoro-1,4-hexadiyne () 6,6-difluoro-1,4-hexadiene (B) 1,1-difluoro-2,5-hexadiyne (D) 6,6-difluoro-1,4-hexadiyne

4 15. The name of the molecule with the con4densed structural formula, H3H(H3)H2H2H(NH2)H3 is: (A) 5-methyl-2-heptanamine () 5-methyl-2-hexanamine (B) 2-methyl-5-hexanamine (D) 5-methylhexanamine 16. Approximately how many atoms are contained in 50. grams of glycerol, 3H8O3.? (A) 1.4 x10 22 (B) 3.3x10 23 () 9.8x10 23 (D) 4.6x Solid aluminum oxide, Al2O3(s), has a density of 3.95 g/cm 3. What is the approximate volume (in in 3 ) of a sample of Al2O3(s) containing 2.5x10 25 Oxygen atoms? (A) 22 in 3 (B) 200 in 3 () in 3 (D) 340 in 3 18 onsider a hypothetical metal, X [with a Molar Mass of 80 g/mol; i.e. M(X)=80.]. A metal sulfide of X has the following percent composition: 78.9% X, 21.1% S. What is the empirical formula of this compound (A) XS2 (B) X3S2 () X2S3 (D) X4S3 19. When 150. grams of a compound containing Phosphorus (P) (and other elements) is burned completely in O2(g), 110 grams of P4O10(s) is produced. Therefore, the percent (by mass) of Phosphorus in this compound is approximately: (A) 32% (B) 9.5% () 8.6% (D) 46% Two (2) Problems on following pages. (You MUST show your work to receive credit)

5 (12) 1. A cylindrical sample of Bismuth(III) Oxide Bi2O3(s) contains 4.3x10 26 atoms of Bismuth atoms. The density of Bi2O3(s) 550 lb/ft 3 (pounds per cubic foot). The height of the cylinder is h = 30. cm. Determine the Radius, R, of the cylindrical face, in cm. Note: The volume of a cylinder is related to the radius of the face, R, and height of 2 the cylinder, h, by: V R h

6 (12) 2. A compound has the following percent composition (by mass): 45.8% Potassium(K), 29.2% Arsenic(As), 25.0% oxygen(o). alculate the empirical formula of this compound.

DO NOT OPEN UNTIL INSTRUCTED TO DO SO. CHEM 100 Dr. McCorkle Exam #2A KEY. While you wait, please complete the following information:

DO NOT OPEN UNTIL INSTRUCTED TO DO SO. CHEM 100 Dr. McCorkle Exam #2A KEY. While you wait, please complete the following information: DO NOT OPEN UNTIL INSTRUTED TO DO SO EM 100 Dr. Mcorkle Exam #2A KEY While you wait, please complete the following information: Name: Student ID: Turn off cellphones and stow them away. No headphones,