NAME ______________________________________________ © Keeney-Kennicutt, 2010 A1 CHEMISTRY 102 FALL 2010 EXAM 1 FORM A SECTION 501 DR. KEENEY-KENNICUTT Directions: (1) Put your name on PART 1 and your name and signature on PART 2 of the exam where indicated. (2) Sign the Aggie Code on PART 2 of this exam. (3) Each multiple choice question is actually 2 questions on your scanning sheet. If you are sure of an answer, put the same answer down for both questions for 5 pts. If you cannot decide between two answers, put your best answer down for the first (odd) question and the other answer down for the second (even) question. If you get the first one correct you'll get 3 pts; if you get the second one correct you’ll get 2 pts. If there is an ambiguous multiple choice question, use the last page to explain your answer. (4) Do NOT write on the envelope. (5) When finished, put everything in the envelope and wait to be excused. At the table, take everything out of the envelope. You can pick up the multiple choice part with the answers outside my office after 3pm. (6) There are a total of 35 questions (19 actual questions). PART 1 1&2. In preparing a solution labeled in molality using a solvent for which the density is unknown, it would NOT be appropriate to measure: (1) total solution volume (2) solute mass (3) solvent volume (4) solvent mass (a) 3,4 (b) 2,3 (c) 1,2 (d) 2,4 (e) 1,3 3&4. Which of the following statements about a mixture of water and benzene, C6H6, is/are TRUE? (1) Benzene, C6H6, and water must have similar polarities because they don’t mix. (2) Both molecules exhibit hydrogen bonding because they both have hydrogens in their formula. (3) A “boundary” will be formed between the two liquids. (a) 1&3 only (b) 3 only (c) 1&2&3 (d) 1&2 only (e) 2 &3 only 5&6. What are the ideal van't Hoff factors for the following compounds: Ba(OH)2, C6H12O6, K2SO4, NaNO3 ? (a) 1, 1, 1, 1 (b) 2, 1, 2, 2 (c) 3, 1, 3, 2 (d) 6, 3, 5, 5 (e) none of the above© Keeney-Kennicutt, 2010 A2 7&8. Which of the following gives an element in its thermodynamic standard state? (a) Sn(aq) (b) Hg(s) (c) K(g) (d) Cl2(g) (e) CO2(g) 9&10. Which observation(s) reflect(s) colligative properties? (1) A 0.5 m copper(II) sulfate solution is blue, while a 0.50 m glucose solution is colorless. (2) A 0.50 m copper(II) sulfate solution has a lower freezing point than a 0.50 m glucose solution. (3) Pure water freezes at a higher temperature than does pure ethanol. (a) only 2 (b) 2,3 (c) only 1 (d) 1&3 (e) only 3 11&12. Which is a FALSE statement about this graph? (a) It can represent how vapor pressure changes with temperature for a pure solvent and a solution. (b) The normal boiling point of the solution is at the intersection between curve D and 760 torr. (c) The boiling point of the pure solvent is about 35oC. (d) The boiling point of a solution is higher than the boiling point of the pure solvent. (e) The rate of evaporation increases with increasing temperature. 13&14. Osmotic pressure is important in maintaining a proper solute concentration across a semipermeable membrane in biological systems. The following statements pertain to osmotic pressure. Which of the following statements is TRUE? (a) Osmotic pressure is the pressure required to prevent the passage of a solute across a semi-permeable membrane because of concentration differences . (b) Solutions of 0.10 M NaCl and 0.10 M C6H12O6 would have the same osmotic pressure. (c) A higher concentration of solute particles creates a lower osmotic pressure. (d) The concentration of solution particles has no effect on the osmotic pressure of a solution. (e) Only the pure solvent molecules will cross a semi-permeable membrane. 15&16. From the table of thermodynamic data, we see that ΔHo f 298 (kJ/mol) for MgO(s) is –601 kJ/mol. This value is the ΔH for the following reaction: (a) Mg(s) + O(g) Æ MgO(s) (b) MgO(s) Æ Mg(s) + ½ O2(g) (c) 2MgO(s) Æ Mg(s) + O2(g) (d) Mg(s) + ½ O2(g) Æ MgO(s) (e) 2Mg(s) + O2(g) Æ 2MgO(s)© Keeney-Kennicutt, 2010 A3 17&18. Which choice includes ALL the following processes that are accompanied by an increase in entropy? (1) I2(s) Æ I2(g) (2) 2I(g) Æ I2(g) (3) 2NH3(g) Æ N2(g) + 3H2(g) (4) Mg2+(aq) + 2OH-(aq) Æ Mg(OH)2(s) (a) 1,2 (b) 1,3 (c) 3,4 (d) 3 (e) 2,4 19&20. Consider the following reaction: X Æ Y with ΔHrxn = +200 kJ and ΔSrxn = –60 J/K. We know: (a) the reaction is exothermic and becoming more ordered (b) the reaction is exothermic and becoming less ordered (c) the reaction is endothermic and becoming more ordered (d) the reaction is endothermic and becoming less ordered (e) it is impossible to know 21&22. Which statement is TRUE? (a) The sign of ∆H determines whether or not a reaction is spontaneous. (b) A synonym for entropy is order. (c) The entropy of any substance is 0 at absolute 0 Kelvin. (d) For a spontaneous reaction, the entropy of the system must increase. (e) The ionization of a weak acid is reactant-favored. 23&24. How many grams of water must be added to 15.0 g of Ca(NO3)2 to prepare a 0.200 m Ca(NO3)2 solution? (a) 0.471 g (b) 19.0 g (c) 75.0 g (d) 214 g (e) 457 g© Keeney-Kennicutt, 2010 A4 25&26. What is the boiling point of an aqueous solution prepared by dissolving 45.0 g of C6H12O6, a non-electrolyte, in 160.0 g of solution? (a) 101.11oC (b) 1.11oC (c) 100.95oC (d) 100.42oC (e) 0.85oC 27&28. Calculate the molarity of a 10.0% MgSO4 solution. The resulting solution has a density of 1.10 g/mL. (a) 0.914 M (b) 0.749 M (c) 0.840 M (d) 0.955 M (e) 0.711 M© Keeney-Kennicutt, 2010 A5 29&30. Consider this process: H2O(g) Æ H2O(l) ∆Hprocess = –44.0 kJ and ∆Sprocess = –119 J/K What is the ∆Suniverse at 25oC and is the reaction spontaneous at 25oC? (a) +370 J/K, no (b) +29 J/K, yes (c) –62 J/K, yes (d) –75 J/K, no (e) +22 kJ/K, no 31&32. An aqueous solution containing 10.5 g of a polymer (nonelectrolyte) in 200. mL of a benzene solution has an osmotic pressure of 0.037 atm at 35oC. What is the apparent formula weight of the polymer? (a) 73,000 g/mol (b) 49,000 g/mol (c) 36,000 g/mol (d) 21,000 g/mol (e) 3,300 g/mol©