ANSWERS CIRCLE CORRECT SECTION

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1 CHEMISTRY EXAM I June 08, 2009 Name: SIGN: RU ID Number Choose the one best answer for each question and write the letter preceding it in the appropriate space on this answer sheet. Only the answer sheet will be graded, so be sure to fill it in clearly and carefully. Illegible answers will be graded as incorrect. USE CAPITAL LETTERS ONLY. ANSWERS Section B-1 Section B-2 CIRCLE CORRECT SECTION Note: See last page of the exam package for periodic table, equations, constants, and other information. Last Name Initial

2 NOTE: FILL IN THE COVER SHEET COMPLETELY BEFORE STARTING THE EXAM TO AVOID PENALTY. 1. A metal fluoride MF 2 crystallizes with a cubic unit cell such that the metal ions, M 2+, occupy the center of two faces and all corners while the fluoride ions, F -, are in the interior of the unit cell. What is the total number of ions in the unit cell? A. 3 B. 5 C. 2 D. 9 E A sample of 200 g of water at 1 atm and 20 C absorbs 120 kj of heat. What mass of water will evaporate? s water = 4.18 J/g. C, s steam = 2.04 J/g. C, H vap of water = 40.7 kj/mol A g B g C g D g E g 3. The vapor pressure of pure water at 25 C is mm Hg. What is the vapor pressure, in mm Hg, of water above a solution that is m glucose, C 6 H 12 O 6? A B C D E

3 4. In which of the following groups of substances would dispersion forces be the only significant factors in determining boiling points? I. Cl 2 II. HF III. Ne IV. KNO 2 V. CCl 4 A. II, V B. III, IV, V C. II, IV D. I, II, III E. I, III, V 5. The molar volume of a certain form of solid lead is 18 cm 3 /mol. Assuming cubic closest packed structure, determine the volume of a single cell. A x 10 6 pm 3 B x 10 8 pm 3 C x 10 4 pm 3 D x 10 2 pm 3 E. none of these 6. At a pressure of O 2 of 1.00 atm, the mole fraction of dissolved O 2 in water is 1.6 x 10-5 at 333 K. What pressure of O 2 would be required to have a solution of 1.5 x 10-3 g O 2 in 250 g H 2 O at 333 K? MM O 2 = g/mol. A atm B atm C atm D atm E atm 7. A solution has a 1:3 mole ratio of cyclopentane to cyclohexane. The vapor pressures of the pure compounds at 25 C are 331 mm Hg for cyclopentane and 113 mm Hg for cyclohexane. What is the mole fraction of cyclopentane in the vapor above the solution? A B C D E

4 8. Which statement is not correct? A. The equilibrium vapor pressure above a liquid is independent of the volume of liquid present and the volume of vapor present. B. The stronger the intermolecular forces, the higher the boiling point. C. A volatile liquid has a high boiling point. D. The boiling point of a liquid is the temperature at which its vapor pressure is equal to the external pressure. E. The vapor pressure above a liquid increases with temperature. 9. How much heat is released when mol of CaCl 2 (s) is dissolved in water? For CaCl 2 : H Latt = kj/mol, H Hyd = kj/mol A kj B kj C kj D kj E kj 10. The unit cell in a certain lattice consists of a cube formed by an anion at each corner, an anion in the center, and a cation at the center of each face. The simplest formula for the compound is A. C 2 A 2 B. C 4 A 3 C. C 6 A 5 D. C 3 A 5 E. C 3 A The molality of an aqueous solution is 1.45 m and it contains 250 g of water. How much water must be added to the solution to reduce its molality to m? A. 136 g B g C g D. 405 g E. 253 g 4

5 12. Which is the most likely order in which the solubility of the following solutes increases in CS 2 ( )? A. W Y Z X B. W Y X Z C. Y X W Z D. X Z Y W E. X Y Z W W. NaCl X. CO 2 Y. NH 3 Z. CH 3 OCH Silver chloride crystallizes with the sodium chloride (rock salt) structure. The length of a unit cell edge is 555 pm. What is the density of AgCl? A g/cm 3 B g/cm 3 C g/cm 3 D g/cm 3 E g/cm A solution is prepared by mixing 20.0 ml 0f M NaCl(aq) and 50.0 ml of M Na 3 PO 4 (aq) solutions. What is the molarity of the Na + (aq) ions in the final solution? Assume both salts ionize completely. A M B M C M D M E M 15. Which solution has the highest boiling point? A m NaCl B m (NH 4 ) 3 PO 4 C m HCl D. 0.1 m urea, CO(NH 2 ) 2 E m CaCl 2 5

6 16. A certain substance, X, has a triple point temperature and pressure of 20 C and 2.0 atm. The equilibrium line between solid and liquid phase has a positive slope. Which one of the following statements can not be true? A. X can exist as a liquid at 25 C and 1 atm. B. X can exist as a solid below 20 C and 2 atm. C. X can not exist as a liquid below 2 atm. D. X can exist as a solid above 20 C. E. X can exist as a liquid above 20 C. 17. When g of NH 4 NO 3 was added to g of water in a container, the temperature dropped by C. The heat capacity of H 2 O is 4.18 J/g C. Assume the specific heat of the solution equals that of pure H 2 O and that the container neither absorbs nor leaks heat. The molar heat of the solution of solid NH 4 NO 3 ( H soln ) is: A kj/mol B kj/mol C. none of these D J/mol E kj/mol 18. Which one of the following aqueous solutions has the lowest freezing point? Assume all solutions behave ideally. A m FeCl 3 B m MgBr 2 C m KF D m HCl E m C 6 H 12 O 6 6

7 19. The volume of one atom of a metal is 3.57 x 10 5 pm 3. The metal has fcc crystal structure. What is the volume of a unit cell? A x 10 5 pm 3 B x 10 6 pm 3 C x 10 6 pm 3 D x 10 6 pm 3 E x 10 5 pm The pair of molecules that form hydrogen bonds between them is: A. W and X B. X and Y C. X and Z D. W and Z E. Y and Z W. CH 3 OH X. CH 4 Y. PH 3 Z. N 2 H 4 7

8 CONSTANTS Summer 2009 N A = x mol -1 R = L atm mol -1 K -1 1 atm = 760 Torr R = 8.31 J mol -1 K -1 1 m = pm EQUATIONS K = C; PV = nrt; q = ms T or n H 4r = 2, 2 or 3 ; V = (4/3) r 3, 2r + + 2r - = or 3, packing fraction = 0.524, or d = (# atoms/u.c.)(m.m.)/n A M mol solute L solution ; m mol solute kg solvent ; X A n n A A n B Sol A = k H P A ; P A = X A P A o ; T = ikm ; = imrt i = 1 + f (i Ideal - 1) place periodic table here 8

PLEASE DO NOT MARK ON THE EXAM. ALL ANSWERS SHOULD BE INDICATED ON THE ANSWER SHEET. c) SeF 4

Chem 130 EXAM 4 Fall 99 PLEASE DO NOT MARK ON THE EXAM. ALL ANSWERS SHOULD BE INDICATED ON THE ANSWER SHEET QUESTIONS 1-5 MAY HAVE MORE THAN ONE POSSIBLE ANSWER CIRCLE ALL CORRECT RESPONSES TO EACH QUESTION