Spring 2009 CH302 Practice Exam 1 1. In general, increasing the temperature favors which phase changes? 1. sublimation, vaporization, fusion 2. sublimation, vaporization, condensation 3. fusion, vaporization, deposition 4. vaporization, freezing, deposition 5. freezing, deposition, condensation 2. Vapor pressure: A. Is an equilibrium process B. increases as IMF increases C. is temperature dependent D. is higher in CH3CH3 than H2 E. decreases with the addition of solutes F. depends on the whole volume of the liquid G. decreases at temp increases 1.A, C, E, G 2. A, B, C, E 3. A, C, D, E 4. B, D, F, G 5. A, C, E 6. A, C, E, F 3. Rank the following in decreasing order of solubility in water: Mg(OH)2, NaCl, Al2O3, CsI, BeBr2, KOH, BaO. 1. Al2O3 > BaO> Mg(OH)2> BeBr2> KOH> NaCl> CsI 2. NaCl> CsI> KOH> BeBr2>Mg(OH)2> BaO> Al2O3 3. Al2O3 > BaO> Mg(OH)2> BeBr2> KOH> NaCl> CsI 4. CsI > NaCl> KOH> BeBr2> Mg(OH)2> BaO> Al2O3 5. NaCl> CsI> BeBr2> KOH> Mg(OH)2> BaO> Al2O3 6. CsI > NaCl> BeBr2> KOH> Mg(OH)2> BaO> Al2O3 4. According to the given phase diagram for carbon, how many triple points are there? What would you expect to see at 0.01GPa, 4500K? 1. 5; metastable liquid, graphite and liquid 2. 4; graphite, metastable liquid and vapor. 3. 5; vapor, metastable liquid, graphite. 4. 4; graphite, liquid, diamond. 5. 3; graphite, metastable liquid and vapor. 5. According to the given pressure-temperature diagram, a sample of carbon at 0.005GPa and 2000K is graphite. This sample is then heated to 7000K at constant pressure. Then, at constant temperature, the sample is compressed to 1.00GPa. Again, at constant pressure, the temperature is decreased to 1000K. At this temperature, the pressure is increased to 500GPa. How many phase transitions has the carbon sample undergone? 1. 6 2. 4 3. 1 4. 5 5. 76. How much heat is generated when 10g steam at 115 oC is cooled to -75 oC? Cice = a J/g oC; Cwater = b J/g oC; Csteam = c J/g oC; ΔHvap = d J/g; ΔHfus = e J/g. 1. q = - [150(5a + c) + 10(100b + d + e)] J 2. q = [150(5a + c) + 10(100b + d + e)] J 3. q = -[150(a + c) + 10(100b + d + e)] J 4. q = [150 (a + c) + 1000b] J 5. q = - [150 (5a + c) + 1000b] J 7. Which solvent would you expect BH3 gas to be most soluble in? 1. C6H6 2. H2O 3. CH3CH2OH 4. CH2Cl2 5. N(CH3)3 8. Rank the following in decreasing order of miscibility with water: H2O2, C6H6, HOCH2CH2NH2, C2H6Cl2, and CH3CH2CH2SH. 1. H2O2 > HOCH2CH2NH2 > CH3CH2CH2SH > C2H6Cl2 > C6H6 2. HOCH2CH2NH2 > H2O2 > C2H6Cl2 > CH3CH2CH2SH > C6H6 3. H2O2 > HOCH2CH2NH2 > C2H6Cl2 > CH3CH2CH2SH > C6H6 4. C6H6 > CH3CH2CH2SH > C2H6Cl2 > HOCH2CH2NH2 > H2O2 5. C6H6 > CH3CH2CH2SH > C2H6Cl2 > H2O2 > HOCH2CH2NH2 9. At 25 C, the vapor pressure of pure benzene (C6H10) is 0.1252 atm. Suppose 6.4 g of napthalene, C10H8, is dissolved in 78 g of benzene (benzene’s molar mass is 78 g/mol). Assuming ideal behavior, what is the vapor pressure of benzene over the solution? 1. 0.9525 atm 2. 0.119 atm 3. 0.1252 atm 10. Water has a vapor pressure of 24 mmHg at 25 °C and a heat of vaporization of 40.7 kJ/mol. What is the vapor pressure of water at 67 °C? 1. 182 mmHg 2 3.15 mmHg 3. 760 mmHg 4. 0 mmHg 11. For the following made-up reaction, where K200K = 0.0035 and K300K = 0.38, solve for the enthalpy change for the reaction. A + X <-> AX 1. ΔH = 23.3 kJ/mol2. ΔH = -48 kJ/mol 3. ΔH = 48 kJ/mol 4. ΔH = -23.3 kJ/mol 12. The vapor pressure is always less above the (pure solvent or dilute solution) than it is above the (pure solvent or dilute solution). 1. dilute solution, pure solvent 2. pure solvent, dilute solution 13. If you add 45 g of NaCl to 500 g of water, what will the melting and boiling points be of the resulting solution? For liquid water, Kb = 0.52 C/m and Kf = 1.86 C/m. Answer should be in the form of (melting pt, boiling pt) 1. 101.6 C, 5.73 C 2. 5.73 C, 101.6 C 3. -5.73 C, 101.6 C 4. -5.73 C, 98.4 C 14. Iron thiocyanate (FeSCN2+) is a complex ion that appears orange-red in solution Iron (III) and thiocyanate ions are both colorless in solution. All species are aqueous. FeSCN2+ <-> Fe3+ + SCN- Set up the equilibrium expression for the reaction: 1. K = [FeSCN2+]/[Fe3+] [SCN-] 2. K = [Fe3+] [SCN-]/ [FeSCN 2+] 3. K = [Fe3+]3 [SCN-]/ [FeSCN2+]2 4. K = [FeSCN2+]2/[Fe3+]3 [SCN-] 15. For the decomposition of gaseous water into hydrogen and oxygen gas, K= 8 X 10-41 With this information, is water a good source of oxygen at room temperature? 1. Yes 2. No 16. The gas-phase dissociation of phosphorus pentachloride to the trichloride has Kp = 3.60 at 540°C: PCl5 PCl3 + Cl2 What will be the partial pressures of all three components if 0.200 mole of PCl5 and 3.00 moles of PCl3 are combined and brought to equilibrium at this temperature? 1. P(PCl5) = 2 atm, P(PCl3) = 3 atm, P(Cl2) = 0 atm2. P(PCl5) = 3.159, P(PCl3) = 1.41 atm, P(Cl2) = 0 .159 atm 3. P(PCl5) = 0.41 atm, P(PCl3) = 4.59 atm, P(Cl2) = 1.59 atm 4. P(PCl5) = 0.041 atm, P(PCl3) = 3.159 atm, P(Cl2) = 0.159 atm 17. For the following reaction, the partial pressures of carbon dioxide, water, methane, and oxygen all are the same at equilibrium. What is their partial pressure? CH4 (g) + 2O2 (g) <-> CO2 (g) + H2O (g) Keq = 5 1. 1 atm 2. 5 atm 3. 10 atm 4. 0.2 atm 5. 0.1 atm 18. For the following reaction, C4H8 (s) + 6O2 (g) <-> 4CO2 (g) + 4H2O (g), Keq = 10 atm. The initial pressures of oxygen, carbon dioxide, and water are 1 atm, 0.5 atm, and 0.5 atm respectively. Which of the following is true for this system? 1. To approach equilibrium, the reaction must shift left 2. More butene (C4H8) needs to be oxidized to reach equilibrium 3. A reagent that removes water vapor would help the system reach equilibrium faster 4. The reaction is now at equilibrium 5. Both 2 and 3 are true 19. For the reaction 3A (g) + B(g) <-> C (s) +D (g), ∆H = -100 J. Which of the following would minimize the formation of C? I. Decreasing the volume of the container II.
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