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CHEM 1515.001 - 006 Exam !V John V. Gelder May 6, 2002 Name ________________________ TA's Name ________________________ Section _______ INSTRUCTIONS: 1. This examination consists of a total of 11 different pages. The last four pages include a periodic table; many useful equations and constants; a table of vapor pressures for water; a solubility table; a table of equilibrium constants for acids and bases; and a table of thermodynamic values. All work should be done in this booklet. 2. PRINT your name, TA's name and your lab section number now in the space at the top of this sheet. DO NOT SEPARATE THESE PAGES. 3. Answer all questions that you can and whenever called for show your work clearly. Your method of solving problems should pattern the approach used in lecture. You do not have to show your work for the multiple choice or short answer questions. 4. No credit will be awarded if your work is not shown in 6. 5. Point values are shown next to the problem number. 6. Budget your time for each of the questions. Some problems may have a low point value yet be very challenging. If you do not recognize the solution to a question quickly, skip it, and return to the question after completing the easier problems. 7. Look through the exam before beginning; plan your work; then begin. 8. Relax and do well. SCORES Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 TOTAL _____ (18) _____ (16) _____ (16) _____ (18) _____ (20) _____ (12) ______ (100) CHEM 1515 EXAM V (9) PAGE 2 1. Write the chemical formula(s) of the product(s) and balance the following reactions. Identify all products phases as either (g)as, (l)iquid, (s)olid or (aq)ueous. Soluble ionic compounds should be written in the form of their component ions. a) Zn(NO3)2(aq) + b) Na2CO3(s) c) (CH3)2NH(aq) + Na2S(aq) Æ HCl(aq) Æ + HCN(aq) Æ (4) 2a. Write the ionic and net ionic chemical equation for 1a), 1b) or 1c). Ionic equation Net Ionic equation (5) 3. Account for the following observations about NH3 and NF3. In your answer, use appropriate principles of intermolecular forces. Your answer must include reference to both substances. a) NH3 has a normal boiling point of –33.4 ˚C where as NF3 has a boiling point of –128.8 ˚C. CHEM 1515 EXAM V PAGE 3 (16) 4. 0.10 M NaF 0.10 M MgCl2 0.10 M C2H5OH 0.10 M CH3COOH (HC2H3O2) Answer the following questions, which refer to the 100 mL samples of aqueous solutions at 25 ˚C in the stoppered flasks shown above (a) Which solution has the lowest electrical conductivity? Explain. (b) Which solution has the lowest freezing point? Explain. (c) Above which solution is the pressure of water vapor the greatest? Explain. (d) Which solution has the highest pH? Explain. CHEM 1515 EXAM V PAGE 4 (16) 5a. Define the term 'equilibrium vapor pressure'. (b) If a sample of a liquid is injected into an evacuated container, describe what phase change occurs. (Note the amount of the liquid injected is small compared to the volume of the container.) (c) Is the phase change exothermic or endothermic? Explain? (d) In terms of the 'pressure exerted by the vapor' and the 'equilibrium vapor pressure' how do we determine what phase(s) are present in the container after adding the sample? CHEM 1515 EXAM V PAGE 5 (18) 6. A commercial aqueous solution of ammonia is 28% NH3 by mass and has a density of 0.900 g mL-1. (a) Calculate the molarity of the solution. (b) Calculate the molality of the solution. (c) Describe how you would prepare 1.00 L of a 0.400 M NH3 solution from the more concentrated solution in part a). CHEM 1515 EXAM V PAGE 6 6. (CONTINUED) (10) (d) Calculate the pH of the solution prepared in part c) . (10) (e) Calculate the pH of the solution prepared by adding 0.250 mol of solid NH4Cl to the solution prepared in part c). CHEM 1515 EXAM V PAGE 7 (12) 7. For the gaseous equilibrium represented below, it is observed that greater amounts of PCl3 and Cl2 are produced as the temperature is increased. PCl3(g) ä PCl3(g) + Cl2(g) (a) What is the sign of ∆S˚ for the reaction? Explain. (b) What change, if any, will occur in ∆G˚ for the reaction as the temperature is increased? Explain your reasoning in terms of thermodynamic principles. (c) If the volume of the reaction mixture is decreased at constant temperature to half the original volume, what will happened to the number of moles of Cl2 in the reaction vessel? Explain. CHEM 1515 EXAM V PAGE 8 Periodic Table of the Elements IA VIIIA 1 1 H 1.008 3 2 He IIA IIIA IVA VA VIA VIIA 4.00 4 5 Li Be 2 B 6.94 9.01 11 12 Na Mg 3 22.99 24.30 19 20 4 5 6 7 6 7 8 9 10 C N O F Ne Al Si P S Cl Ar 31 33 34 35 10.81 12.01 14.01 16.00 19.00 20.18 13 14 15 16 17 18 IIIB IVB VB VIB VIIB 21 22 K Ca Sc Ti 23 24 25 VIII 26 27 IB 28 29 IIB 26.98 28.09 30.97 32.06 35.45 39.95 30 32 36 V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 39.10 40.08 44.96 47.88 50.94 52.00 54.94 55.85 58.93 58.69 63.55 65.38 69.72 72.59 74.92 78.96 79.90 83.80 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 85.47 87.62 88.91 91.22 92.91 95.94 (98) 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.3 55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 132.9 137.3 138.9 178.5 180.9 183.8 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 (209) (210) (222) 87 88 89 104 105 106 Fr Ra Ac (223) 226.0 227.0 (261) (262) (263) Lanthanides Actinides 58 59 60 61 62 63 64 65 66 67 68 69 70 71 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 140.1 140.9 144.2 (145) 150.4 152.0 157.2 158.9 162.5 164.9 167.3 168.9 173.0 175.0 90 91 92 93 94 95 96 97 98 99 100 101 102 103 Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr 232.0 231.0 238.0 237.0 (244) (243) (247) (247) (251) (252) (257) (258) (259) (260) Useful Information L·atm J PV = nRT R = 0.0821 mol·K = 8.314 mol·K Ê vp2ˆ ∆H˚vap Ê 1 1ˆ g lnÁË vp1˜¯ = – R ÁË T2!–!T1˜¯ density of H2O = 1.00 3 cm ∆H˚rxn = ∑n(∆Hf˚(products)) – ∑ m(∆Hf˚(reactants)) 6.02 x 1023 ∆S˚rxn = ∑ n(S˚(products)) – ∑ m(S˚(reactants)) ∆G˚rxn = ∑ n(∆Gf˚(products)) – ∑ m(∆Gf˚(reactants)) ∆G˚ = ∆H˚ - T∆S˚ pH = –log[H+ ] ∆G˚ = –RTlnK x1,2 = pH + pOH = 14 Kp = Kc(RT)∆n –b± b2!–!4ac for ax2 + bx + c = 0 2a pOH = –log [OH–] Kw = 1.00 x 10–14 CHEM 1515 EXAM V PAGE 9 1 pm = 10-12 m Psolution = csolventP˚solvent ∆T = ikm ˚C kf(H2O) = 1.86 m edge length (l) = 2r ˚C kb(H2O) = 0.512 m edge length (l) = 2 2· r Temperature (°C) -5 0 5 10 15 20 25 30 35 40 45 Vapor Pressure(mmHg) 3.2 4.6 6.52 9.20 12.8 17.5 23.8 31.8 42.1 55.3 71.9 edge length (l) = Temperature (°C) 50 55 60 65 70 75 80 85 90 95 100 4r 3 Vapor Pressure(mmHg) 92.5 118.0 149.4 187.5 233.7 289.1 355.1 433.6 525.8 633.9 760 Solubility Table Ion NO3– ClO4– Cl– I– SO42– Solubility soluble soluble soluble soluble soluble Exceptions none none except Ag+ , Hg22+, *Pb2+ except Ag+ , Hg22+, Pb2+ except Ca2+, Ba2+, Sr2+, Hg2+, Pb2+, Ag+ CO32– insoluble except Group IA and NH4 PO43– -OH S2– Na+ NH4+ K+ insoluble insoluble insoluble soluble soluble soluble except Group IA and NH4 except Group IA, *Ca2+, Ba2+, Sr2+ except Group IA, IIA and NH4+ none none none *slightly soluble + + CHEM 1515 EXAM V Name PAGE 10 Formula Ka1 Acetic Ascorbic HC2 H3 O2 Arsenic H3 AsO4 1.8 x 10– 5 8.0 x 10– 3 5.6 x 10– 3 Arsenous Benzoic Boric Butyric acid Carbonic Cyanic Citric H3 AsO3 HC7 H5 O2 H3 BO3 HC4 H7 O2 H2 CO3 HCNO H3 C6 H5 O7 6.0 6.5 5.8 1.5 4.3 3.5 7.4 Formic Hydroazoic Hydrocyanic Hydrofluoric Hydrogen chromate ion Hydrogen peroxide Hydrogen selenate ion Hydrogen sulfate ion Hydrogen sulfide Hypobromous Hypochlorous Hypoiodus Iodic Lactic Malonic Oxalic HCHO2 HN3 HCN HF HCrO4 – H2 O2 HSeO4 – HSO4 – H2 S HBrO HClO HIO HIO3 HC3 H5 O3 H2 C3 H2 O4 H2 C2 O4 1.8 1.9 4.9 7.2 3.0 2.4 2.2 1.2 5.7 2.0 3.0 2.0 1.7 1.4 1.5 5.9 Nitrous Phenol Phosphoric Paraperiodic Propionic Pyrophosphoric Selenous Sulfuric Sulfurous Tartaric HNO2 HC6 H5 O H3 PO4 H5 IO6 HC3 H5 O2 H4 P2 O H2 SeO3 H2 SO4 H2 SO3 H2 C4 H4 O6 E.2 HC6 H7 O6 10– 1 0 10– 5 10– 1 0 10– 5 10– 7 10– 4 10– 4 x 10– 4 x 10– 5 x 10– 1 0 x 10– 4 x 10– 7 x 10– 1 2 x 10– 2 x 10– 2 x 10– 8 x 10– 9 x 10– 8 x 10– 1 1 x 10– 1 x 10– 4 x 10– 3 x 10– 2 x 10– 4 x x x x x x x 4.5 1.3 x 7.5 x 2.8 x 1.3 x 3.0 x 2.3 x strong 1.7 x 1.0 x 10– 1 0 10– 3 10– 2 10– 5 10– 2 10– 3 acid 10– 2 10– 3 Ka2 Ka3 1.0 x 10– 7 3.0 x 10– 1 2 5.6 x 10– 1 1 1.7 x 10– 5 4.0 x 10– 7 1.3 x 10– 1 3 2.0 x 10– 6 6.4 x 10– 5 6.2 x 10– 8 5.3 x 10– 9 4.4 5.3 1.2 6.4 4.6 x x x x x 4.2 x 10– 1 3 10– 3 10– 9 10– 2 10– 8 10– 5 DISSOCIATION CONSTANTS FOR BASES AT 25˚C Name Formula Ammonia Aniline Dimethylamine Ethylamine Hydrazine NH3 C6 H5 NH2 (CH3 )2 NH C2 H5 NH2 H2 NNH2 Kb 1.8 4.3 5.4 6.4 1.3 x x x x x 10– 5 10– 1 0 10– 4 10– 4 10– 6 Name Formula Hydroxylamine Methylamine Pyridine Trimethylamine HONH2 CH3 NH2 C5 H5 N (CH3 )3 N Kb 1.1 4.4 1.7 6.4 x x x x 10– 8 10– 4 10– 9 10– 5 CHEM 1515 EXAM V PAGE 11 Thermodynamic Values (25 ˚C) Substance and State Carbon C(s) (graphite) C(s) (diamond) CO(g) CO2 (g) CH4 (g) CH3 OH(g) CH3 OH(l) CH3 Cl(g) CHCl3 (g) CHCl3 (l) H2 CO(g) HCOOH(g) HCN(g) C2 H2(g) C2 H4 (g) CH3 CHO(g) C2 H5 OH(l) C2 H6 (g) C3 H6 (g) C3 H8 (g) Bromine Br2 (l) BrCl(g) o! o! So Substance Ê J ˆ Ë K. mol¯ and State DH f Ê kJ ˆ Ë mol¯ DG f Ê kJ ˆ Ë mol¯ 0 2 -110.5 -393.5 ? -201 -239 -80.8 -100.8 -131.8 -116 -363 135.1 227 52 -166 -278 -84.7 20.9 -104 0 3 -137 -394 -51 -163 -166 -57.4 6 2 198 214 186 240 127 234 -110 -351 125 209 68 -129 -175 -32.9 62.7 -24 219 249 202 201 219 250 161 229.5 266.9 270 0 14.64 0 -0.96 152. 240 Chlorine Cl2 (g) Cl2 (aq) Cl-(aq) HCl(g) 0 -23 0 7 223 121 -167 -92 -131 -95 57 187 Fluorine F2 (g) F-(aq) HF(g) 0 -333 -271 0 -279 -273 203 -14 174 Hydrogen H2 (g) H(g) 217 H+(aq) OH-(aq) H2 O(l) H2 O(g) Magnesium Mg(s) Mg(aq) MgO(s) 0 203 0 -230 0 115 0 -157 131 -242 -229 189 0 -492 -601 0 -456 -569 33 -118 26.9 0 -11 o! o! So DH f Ê kJ ˆ Ë mol¯ DG f Ê kJ ˆ Ë mol¯ 0 232 143 0 161 163 205 Nitrogen N2 (g) NCl3 (g) NF3 (g) NH3 (g) NH3 (aq) NH2 CONH2 (aq) NO(g) NO2 (g) N2 O(g) N2 O4 (g) N2 O5 (g) HNO3 (aq) HNO3 (l) NH4 Cl(s) NH4 ClO4 (s) 0 230 -125 ? ? ? 90 32 82 10 -42 -207 -174 -314 -295 0 271 -83.6 -17 -27 ? 87 52 104 98 134 -111 -81 -201 -89 192 -137 -139 193 111 174 211 240 220 304 178 146 156 95 186 Silver Ag(s) Ag+(aq) Ag(S2 O3 )3-(aq) AgBr(s) AgCl(s) 0 105.6 -1285.7 -100.4 -127.1 0 77.1 --96.9 -109.8 42.6 72.7 -107.1 96.2 Oxygen O2 (g) O(g) 249 O3 (g) Ê J ˆ Ë K. mol¯ 239 Sulfur S(rhombic) SO2 (g) SO3 (g) H2 S(g) 0 -296.8 -395.7 -20.17 0 -300.2 -371.1 -33.0 31.8 248.8 256.3 205.6 Titanium TiCl4 (g) TiO2 (s) -763 -945 -727 -890 355 50 Aluminum AlCl3 (s) -526 -505 184 Barium BaCl2 (aq) -872 Ba(OH)2 ·8H2 O(s) -3342 -823 -2793 123 427 Iodine I2 (s) HI(g) 0 25.94 0 1.30 116.7 206.3