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BU CHEM 108 - Chem 108 Summer 2014 Exam 1

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1 State University of New York at Binghamton, Department of Chemistry Chemistry 108, Introductory Chemistry II, Exam 1, July 14, 2014. The exam will be graded based on the scantron. Only non-graphic calculators are allowed on this exam. You have 90 minutes to complete this exam. DO NOT SEPARATE THE EXAM. Answer ALL questions. Fill in the appropriate selection on your scantron form. 1. The unit cell in a certain lattice consists of a cube formed by a cation at each corner, a cation in the center, and an anion at the center of each face. The unit cell contains a net: A) 5 anions and 6 cations. B) 3 anions and 2 cations. C) 5 anions and 3 cations. D) 2 anions and 2 cations. E) 2 anions and 3 cations. 2. Which of the following concerning solutions is/are correct? 1. The solvent in a mixture of gases is generally considered to be the substance in greater amount. 2. The solid dissolved in a solution is known as the solute. 3. Solid solutions are called alloys. A) only B) 2 only C) 3 only D) 1 and 2 E) 1, 2, and 3 3. An unknown metal crystallizes in a face-centered cubic structure. What is the coordination number of each atom? A) 4 B) 8 C) 12 D) 6 4. Which one of the following liquids would you expect to have the lowest vapor pressure at room temperature? (all boiling points are normal boiling points) A) n-Pentane, b.p. = 36.1°C B) Methanol, b.p. = 65.0°C C) Carbon tetrachloride, b.p. = 76.7°C D) Mercury, b.p. = 357°C E) Acetic acid, b.p. = 118°C2 5. Which of the following processes is endothermic? A) Condensation of ammonia B) Condensation of water C) Deposition of carbondioxide D) Freezing of water E) Melting of ice 6. At a particular temperature the solubility of O2 in water is 0.590 g/L at an oxygen pressure of around 14.7 atm. What is the Henry's law constant for O2 (in units of L · atm/mol)? A) 4.01  10-2 B) 7.97  102 C) 2.71  10-1 D) 1.25  10-3 E) None of the above are within 5% of the correct answer. 7. The metal gold, with an atomic radius of 144.2 pm, crystallizes in a face-centered cubic lattice. What is the density of gold? A) 12.0 g/cm3 B) 0.752 g/cm3 C) 3.01 g/cm3 D) 1.50 g/cm3 E) 6.01 g/cm3 8. Determine the osmotic pressure of a solution that contains 0.014 g of a hydrocarbon solute (molar mass = 340 g/mol) dissolved in benzene to make a 350-mL solution. The temperature is 20.0°C. A) 0.9 torr B) 2.0 torr C) 0.14 torr D) 0.7 torr E) 2.1 torr 9. Indicate which of the following pairs of compounds is most likely to be immiscible. A) H2O and CH3CH2OH B) Br2 and I2 C) HF and CCl4 D) CCl4 and O2 E) CHCl3 and PH33 10. What is the vapor pressure at 20°C of an ideal solution prepared by the addition of 8.87 g of the nonvolatile solute urea, CO(NH2)2, (Mw ~ 60.07 g/mol), to 57.6 g of methanol, CH3OH? The vapor pressure of pure methanol at 20°C is 89.0 mmHg. A) 6.75 mmHg B) 69.1 mmHg C) 77.1 mmHg D) 82.2 mmHg E) 19.9 mmHg 11. What is the simplest formula of the compound represented by the unit cell provided below? (Atoms A on the comers and B on the edges). A) AB3 B) AB2 C) AB D) A2B4 E) A2B6 12. Which of the following statements concerning the accompanying phase diagram is false? A) The solid is more dense than the liquid. B) Point C is the critical point of the substance. C) Point A is the triple point of the substance. D) The normal boiling point is above the triple point. E) The curve AD divides the solid region from the gas region.4 13. A solute added to a solvent raises the boiling point of the solution because A) the temperature to cause boiling must be great enough to boil not only the solvent but also the solute. B) the solute particles raise the solvent's vapor pressure, thus requiring a higher temperature to cause boiling. C) the solute increases the volume of the solution, and an increase in volume requires an increase in the temperature to reach the boiling point (derived from PV = nRT). D) the solute particles lower the solvent's vapor pressure, thus requiring a higher temperature to cause boiling. E) two of these explanations are correct. 14. What is the molality of a solution that contains 8.16 g of glucose, C6H12O6, in 252.5 g of water? A) 0.180 m B) 0.0453 m C) 0.00322 m D) 0.0114 m E) 0.0323 m 15. Knowing that Hvap for water is 40.7 kJ/mol, calculate Pvap of water at 37°C given the normal boiling point of water is 100 oC. A) 25.4 torr B) 6.90 torr C) 52.7 torr D) 18.7 torr E) 12.4 torr 16. Substance A has a greater molar mass than substance B. If 50 g of substance A are dissolved in 250 g of water in one beaker, and 50 g of substance B are dissolved in 250 g of water in another beaker, then_____ (Assume both substance A and B are non-electrolytes) A) the vapor pressure of solution A will be lower than the vapor pressure of solution B. B) the solution of A will freeze at a lower temperature than the solution of B. C) the two solutions will have the same vapor pressure. D) the boiling point of solution A will be lower than the boiling point of solution B. E) the solution of A will have a higher osmotic pressure than the solution of B.5 17. Arrange the three compounds sodium chloride, magnesium chloride, and aluminum chloride in order of decreasing melting point. A) NaCl > MgCl2 > AlCl3 B) MgCl2 > NaCl > AlCl3 C) AlCl3 > MgCl2 > NaCl D) AlCl3 > NaCl > MgCl2 E) NaCl > AlCl3 > MgCl2 18. The vapor pressure of an aqueous solution is found to be 24.9 mm Hg at 25°C. What is the mole fraction of solute in this solution? The vapor pressure of water is 25.756 mm Hg at 25°C. A) 0.976 B) 1.03 C) 0.0332 D) 0.967 E) 0.0344 19. Assuming the following metals all have the same unit cell structure, which of the following would be expected to have the lowest density: Sc, Ti, Mn, or Co? A) Co B) Sc C) Cr D) Ti E) Cannot be determined from the information given. 20. From a consideration of the phase diagram below, a change from point M to point N corresponds to A) Sublimation. B) Liquefaction. C) Evaporation. D) Condensation. E) Freezing.6 21. A saline solution is administered intravenously to patients who cannot take fluid orally and are in danger of dehydration. The osmotic pressure of this solution must match that of blood to prevent hemolysis or crenation of blood cells. What mass of sodium chloride (58.44 g/mol) is needed to produce 100.0 mL of saline solution with an osmotic pressure of 7.83 atm at a body temperature of 37°C? Consider the Vant’ Hoff factor of …


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