Chem 1C - Spring 2010 - exam 2 VERSION B Yellow ON YOUR SCANTRON: BUBBLE IN YOUR 7 DIDGIT PERM (Leaving the last three digits blank) BUBBLE IN THE VERSION: B WRITE YOUR NAME AT THE END, HAND IN ONLY THE SCANTRON. 1234567 perm version name 1
1. What is the molality of a solution of 150 g of NaI in 250 ml water, if the density of water is 1 kg/liter? 250 m 4 m 400 m 15 m 60 m 2. The sizes of the holes in a closest packed structure of ions with radius R are: tetrahedral: 0.225 R octahedral: 0.414 R cubic: 0.732 R Where would counterions with radius of 0.5 R most likely be? in the tetrahedral holes in the octahedral holes in the cubic holes in both tetrahedral and octahedral holes in any of the holes 3. A solution contains 46 g of ethanol (C 2 H 5 OH) and 54 g of water. What is the mole fraction of the ethanol? 2 1 0.75 0.25 0.42 4. As you dilute a solution (adding solvent), which will decrease? mole fraction of solute molality molarity all of the above None of the above 5. Rank the following types of forces in order of increasing strength: ionic < London < Dipole-dipole London < Dipole-dipole < ionic London < ionic < Dipole-dipole ionic < Dipole-dipole < London Dipole-dipole < London < ionic 2
6. A 62.0 g sample of ethylene glycol antifreeze (a nondissociated, nonvolatile solute with the formula C 2 H 4 (OH) 2, molar mass 62) is dissolved in 180 g water. What is the vapor pressure of this solution at 100 C? 760 torr 76 torr 380 torr 1000 torr 691 torr 7. What is the freezing point of the above solution? (K f = 1.8 o C kg/mol)? 1 o C +10 o C 10 o C 18 o C 1.8 o C 8. Pentane (C 5 H 12 ) and hexane (C 6 H 14 ) form an ideal solution. The vapor pressures of pentane and hexane at 25 C are 500 torr and 150 torr, respectively. The mole fraction of hexane in a pentane-hexane solution is 0.50. Calculate the mole fraction of pentane in the vapor in equilibrium at 25 C with this solution. 0.1 0.23 0.50 0.77 1 9. Solutions A and B of the same compound with equal volumes are placed in a closed container. At the start the concentration of solution A is smaller than the concentration of solution B. After a while the vapor pressure reaches equilibrium. Now A B the volumes are equal beaker A is empty. beaker B is empty. the volume in Beaker A is larger than that in beaker B. the volume in Beaker B is larger than that in beaker A. 3
10. At a given temperature, you have a mixture of benzene (Pvap = 750 torr) and toluene (Pvap = 300 torr). You do not know any of the mol fractions. Nevertheless you are asked to pick the possible total vapor pressure from the following choices: 1050 torr 760 torr 500 torr 250 torr 150 torr 11. A cucumber is placed in a concentrated salt solution. What will most likely happen? Salt will precipitate out. Water will flow from the solution to the cucumber. Salt will flow into the cucumber. Water will flow from the cucumber to the solution. No change will occur. 12. The unit cell in a certain lattice of atoms X and Y consists of a cube formed by an X at each corner of the cube, an X at the center of the cube and a Y at the center of each face. The empirical formula of the compound is: XY. X 5 Y 6. X 5 Y 3. X 2 Y 2. X 2 Y 3. 13. Doping Si with B or P would produce the following types of semiconductor: B P n-type n-type p-type n-type n-type p-type p-type p-type none of the above 4
14. What is the electron configuration of the Cr(III) ion in a complex? [Ar]4s 2 4d 1 [Ar]3d 1 4s 2 [Ar]3d 4 4s 2 [Ar]3d 3 [Xe]5d 1 15. The spectrochemical series is I < Br < Cl < F < OH < H 2 O < NH 3 < en < NO 2 < CN Which of the following complexes will absorb visible radiation of the highest energy (shortest wavelength)? [Co(H 2 O)6] 3+ [Co(I) 6 ] 3 [Co(OH) 6 ] 3 [Co(en) 3 ] 3+ [Co(NH 3 ) 6 ] 3+ 16. The color of a transition metal complex results from: bending vibrations. stretching vibrations. transition of an electron between d orbitals. transition of an electron between s and p orbitals. nuclear magnetic resonance. 17. Which ranking of the following compounds is in order of increasing intermolecular forces: I 2 < Cl 2 < CO < H 2 O Cl 2 < I 2 < CO < H 2 O CO < I 2 < H 2 O < Cl 2 H 2 O < Cl 2 < I 2 < CO H 2 O < I 2 < CO < Cl 2 18. Which of the following has the highest boiling point? Xe HCl CO 2 Benzene F 2 5
19. Which of the following has the lowest freezing point? Xe HCl CO 2 Benzene F 2 20. These two [Co(en) 3 ] complexes are. linkage isomers coordination isomers stereo isomers ionization isomers none of the above 21. A hypothetical element has atoms that weigh 10-26 grams each and form an FCC crystal with a unit cell with a volume of 10-26 cm 3. The crystal density is 4 gram/ cm 3 10 26 gram/ cm 3 1 gram/ cm 3 2 gram/ cm 3 0.25 gram/ cm 3 22. How much energy does it take to melt 18 g of water at 0 o C (ΔH fus = 6 kj/mol)? 10 3 J 6 x 10 3 J 10 6 J 3 x 10 6 J 18 x 10 6 J 6
23. Which of the following is pentaamminechlorocobalt(iii) chloride? [Co(NH 3 ) 5 Cl]Cl 5 [Co(NH 3 ) 5 Cl]Cl [Co(NH 3 ) 6 ]Cl 2 [Co(NH 3 ) 5 Cl]Cl 2 [Co(NH 3 ) 6 ]Cl 5 24. Which of the following is polar? F 2 SF 2 SF 6 S 2 None of the above 25. When a substance freezes, what are the signs of the enthalpy change, ΔH and entropy change ΔS? ΔH ΔS positive positive positive negative negative positive negative negative impossible to predict 26. Larger intermolecular forces in a liquid lead to lower vapor pressure larger viscosity lower boiling point and (b) all of the above 27. How many electrons are involved in π bonding in benzene (C 6 H 6 ): 6 12 18 24 30 7
28. What is the hybridization of the carbon atoms in graphite? sp sp2 sp3 sp3d they are not hybedrized 29. Which is closest to the bond angle in ozone, O 3 90 o 109.5 o 120 o 180 o 360 o 30. The bond order of H 2 is 0 0.5 1 1.5 2 31. The solubility of nitrogen in water is 1 10-5 mol/l at 0 C when the N 2 pressure above water is 0.75 atm. What is the solubility of N 2 in water when the partial pressure of nitrogen above water is 1.5 atm at 0 C 0.5 10-5 mol/l 1 10-5 mol/l 2 10-5 mol/l 1 10-10 mol/l 7.5 10-5 mol/l 8
32. Consider the following Lewis structure, in which E is an unknown element E can be H P Be I K 33. The allene molecule has the following Lewis structure: Which of the following statements is false? The center C atom is sp hybridized. The center C atom is involved in two π bonds The outer C atoms are sp2 hybridized All four H atoms are in the same plane The p orbitals on the center C atom are perpendicular to each other BONUS: To prevent crenation or hemolysis, IV (intravenous) solutions must be Hypotonic Hypertonic Equimolar Equidistant Isotonic Don t forget perm, version B, name 9
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