8. Relax and do well.

Transcription

1 CHEM 1515 Name Exam IV TA's Name John IV. Gelder December 14, 1993 Lab Section INSTRUCTIONS: 1. This examination consists of a total of 9 different pages. The last 4 pages include important mathematical equations and constants, a periodic table, and a table of solubility equilibrium constants, standard thermodynamic values and standard reduction potentials. All work should be done in this booklet. You may carefully remove the last 4 pages of the examination. 2. PRINT your name, your TA's name and your laboratory section now in the space at the top of this sheet. DO NOT SEPARATE THE 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 problems 2 5, 7 and 8. Please circle your final answer! 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. Page 2 Page 3 Page 4 Page 5 TOTAL SCORES (21) (24) (26) (29) (100)

2 CHEM 1515 Exam IV F93 Page 2 (9) 1. Write the chemical formula(s) of the product(s) and balance the following reactions. Identify the phase of each product 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) Ca(OH) 2 (s) + NH 4 Cl(s) b) Zn(s) + HCl(aq) c) Cu(NO 3 ) 2 (aq) + Mg(s) (12) 2. Balance the following oxidation-reduction reaction using the half-reaction method. a) ClO (aq) + CrO 2 (aq) Cl (aq) + CrO4 2 (aq) basic solution identify the oxidizing agent identify the reducing agent

3 CHEM 1515 Exam IV F93 Page 3 (24)3a. Calculate G rxn, H rxn and S rxn for the reaction NO 2 (g) + N 2 O(g) 3NO(g) b) What would be the values of these three functions at 400 C. (Note: State any assumptions.) c) What is the magnitude of the equilibrium constant, K p, for the reaction at 25 C? d) Is the reaction spontaneous at 25 C? How would an increase in the temperature effect the spontaneity of the reaction? At what temperatures is the reaction spontaneous?

4 CHEM 1515 Exam IV F93 Page 4 (16)4a. Calculate the solubility of PbI 2 in pure water at 25 C. b) Calculate the solubility of PbI 2 in M CaI 2. (10) ml of M AgNO 3 are mixed with ml of M ZnCl 2. a) Write the chemical equation which describes the reaction which will occur when the two solutions are mixed. b) Calculate the equilibrium concentrations of Ag + (aq), NO 3 (aq), Zn 2+, and Cl.

5 CHEM 1515 Exam IV F93 Page 5 (9) 6. Write the chemical formula(s) of the product(s) and balance the following reactions. a) Sr(s) + Mg 2+ (aq) b) Cl (aq) + MnO 4 (aq) + H + (aq) c) Ag(s) + HCl(aq) (4) 7. Write the half-reactions and determine E for the electrochemical cell as described below, include the overall chemical equation. Zn(s) Zn 2+ (aq) Cr 2 O 7 2 (aq), H + (aq), Cr 3+ (aq) Pt(s) (16) 8. Given the two half-reactions MnO 4 (aq) + 8H + (aq) + 5e Mn 2+ (aq) + 4H 2 O(l) O 2 (g) + 2H + (aq) + 2e H 2 O 2 E = v E = v Write the chemical equation for the spontaneous reaction which can occur. Calculate the E, K and G for the spontaneous reaction.

6 CHEM 1515 Exam IV F93 Page 6 Equations Useful Information Constants H rxn = ( H f (products)) ( H f (reactants)) S rxn = (S (products)) (S (reactants)) G rxn = ( G f (products)) ( G f (reactants)) 1 amp sec = 1 coulomb G = H - T S G = RT ln K G = G + RT ln Q ph = log[h + ] G = nfe J F = 96,500 volt mol E cell = E n ln Q E = n ln K R = L. atm mole. K = E cell = E n log Q E = n log K = 96,500 coulombs J mole. K IA 1 H Li IIA 4 Be Na Mg K Ca Rb Sr Cs Ba Fr (223) Ra IIIA IVA VA VIA VIIA B C N O F 9 10 Ne IIIB IVB VB VIB VIIB VIII IB IIB Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe (98) La Periodic Table of the Elements Hf Al Si P S Cl VIIIA 2 Ta W Re 75 Os Ir Pt Au Hg 80 Tl Pb Bi Po At Rn (209) (210) Ac Rf Db Sg Bh Hs Mt (261) (262) (263) (262) (265) (266) He Ar (222) Lanthanides Actinides Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu (145) Th Pa U Np Pu AmCm Bk Cf Es Fm Md No Lr (244) (243) (247) (247) (251) (252) (257) (258) (259) (260)

7 CHEM 1515 Exam IV F93 Page 7 E. 3 SOLUBILITY-PRODUCT CONSTANTS FOR COMPOUNDS AT 25 C Name Formula K sp Barium carbonate BaCO x 10-9 Barium chromate BaCrO x Barium Fluoride BaF x 10-6 Barium hydroxide Ba(OH) 2 5 x 10-3 Barium oxalate BaC 2 O x 10-7 Barium phosphate Ba 3 (PO 4 ) x Barium sulfate BaSO x Cadmium carbonate CdCO x Cadmium hydroxide Cd(OH) x Cadmium sulfide CdS 8.0 x Calcium carbonate CaCO x 10-9 Calcium chromate CaCrO x 10-4 Calcium fluoride CaF x Calcium hydroxide Ca(OH) x 10-6 Calcium phosphate Ca 3 (PO 4 ) x Calcium sulfate CaSO x 10-6 Cerium(III) fluoride CeF 3 8 x Chromium(III) fluoride CrF x Chromium(III) hydroxide Cr(OH) x Cobalt(II) carbonate CoCO x Cobalt(II) hydroxide Co(OH) x Cobalt(III) hydroxide Co(OH) x Copper(I) bromide CuBr 5.3 x 10-9 Copper(I) chloride CuCl 1.2 x 10-6 Copper(I) sulfide Cu 2 S 2.5 x Copper(II) carbonate CuCO x Copper(II) chromate CuCrO x 10-6 Copper(II) hydroxide Cu(OH) x Copper(II) phosphate Cu 3 (PO 4 ) x Copper(II) sulfide CuS 6.3 x Gold(III) chloride AuCl x Iron(II) carbonate FeCO x Iron(II) hydroxide Fe(OH) x Iron(II) sulfide FeS 6.3 x Iron(III) hydroxide Fe(OH) 3 4 x Lanthanum fluoride LaF 3 7 x Lanthanum iodate La(IO 3 ) x Lead carbonate PbCO x Lead chloride PbCl x 10-5 Lead chromate PbCrO x Lead fluoride PbF x 10-8 Lead hydroxide Pb(OH) x Lead iodide PbI x 10-9 Lead sulfide PbS 8.0 x Magnesium hydroxide Mg(OH) x Magnesium oxalate MgC 2 O x 10-5 Manganese carbonate MnCO x Mercury(I) sulfide Hg 2 S 1.0 x Mercury(II) sulfide HgS 4.0 x Silver chloride AgCl 1.8 x Silver sulfide Ag 2 S 6.3 x Strontium fluoride SrF x 10-9

8 CHEM 1515 Exam IV F93 Page 8 Substance H o f and State kj G o f kj J K. mol Carbon C(s) (graphite) C(s) (diamond) CO(g) CO2(g) CH4(g)? CH3OH(g) CH3OH(l) H2CO(g) HCOOH(g) HCN(g) C2H2(g) C2H4(g) CH3CHO(g) C2H5OH(l) C2H6(g) C3H6(g) C3H8(g) S o mol mol Thermodynamic Values (25 C) Substance H o f and State kj G o f kj S o J K. mol mol mol Nitrogen N2(g) NCl3(g) NF3(g) NH3(g)? NH3(aq)? NH 2 CONH2(aq)?? 174 NO(g) NO2(g) N2O(g) N2O4(g) N2O5(g) N2H3CH3(l) HNO3(aq) HNO3(l) NH4Cl(s) NH4ClO4(s) Bromine Br2(l) BrCl(g) Chlorine Cl2(g) Cl2(aq) Cl - (aq) HCl(g) Fluorine F 2 (g) F - (aq) HF(g) Hydrogen H2(g) H(g) H + (aq) OH - (aq) H2O(l) H2O(g) Magnesium Mg(s) Mg(aq) MgO(s) Oxygen O2(g) O(g) O3(g) Silver Ag(s) Ag + (aq) Ag(S2O3) 3- (aq) AgBr(s) AgCl(s) Sulfur S(rhombic) SO 2 (g) SO 3 (g) H 2 S(g) Titanium TiCl4(g) TiO2(s) Aluminum AlCl3(s) Barium BaCl2(aq) Ba(OH)2 8H2O(s) Iodine I2(s) HI(g)

9 CHEM 1515 Exam IV F93 Page 9 Table of Standard Reduction Potentials (25 C)

10 CHEM 1515 Exam IV F93 Page 10 A. Acidic Solution E o (V) Li + + e Li(s) K + + e K(s) Ba e Ba(s) Sr e Sr(s) Ca e Ca(s) Na + + e Na(s) Mg e Mg(s) H 2 (g) + 2e 2H 2.25 Al e Al(s) Mn e Mn(s) Zn e Zn(s) Cr e Cr(s) Fe e Fe(s) Cr 3+ + e Cr Cd e Cd(s) PbSO 4 (s) + 2e Pb(s) + SO PbCl 2 (s) + 2e Pb(s) + 2Cl Ni e Ni(s) Sn e Sn(s) Pb e Pb(s) H + + 2e H 2 (g) S(s) + 2H + + 2e H 2 S(aq) Sn e Sn Sb 2 O 3 (s) + 6H + + 6e 2Sb(s) + 3H 2 O(l) Cu 2+ + e Cu SO H + + 2e H 2 SO 3 (aq) + H 2 O(l) AgCl(s) + e Ag(s) + Cl Cu e Cu(s) SO H + + 6e S(s) + 4H 2 O(l) H 2 SO 3 (aq) + 4H + + 4e S(s) + 3H 2 O(l) I 2 (s) + 2e 2I MnO 4 + e MnO [PtCl 6 ] 2 + 2e [PtCl 4 ] 2 + 2Cl 0.68 O 2 (g) + 2H + + 2e H 2 O 2 (aq) Fe 3+ + e Fe Hg e Hg(l) Ag + + e Ag(s) NO 3 + 4H + + 2e N 2 O 4 (g) + 2H 2 O(l) Hg e Hg NO 3 + 4H + + 3e NO(g) + 2H 2 O(l) 0.96 Pd e Pd(s) Br 2 (l) + 2e 2Br Br 2 (aq) + 2e 2Br ClO 4 + 2H + + 2e ClO 3 + H 2 O(l) IO H e I 2 (s) + 6H 2 O(l) Pt e Pt(s) ~1.2 ClO 3 + 3H + + 2e HClO 2 (aq) + H 2 O(l) 1.21 O 2 (g) + 4H + + 4e 2H 2 O(l) O 2 (g) + 4H + (ph = 7) + 4e 2H 2 O(l) 0.83 MnO 2 (s) + 4H + + 2e Mn H 2 O(l) HNO 2 (aq) + 4H + + 4e N 2 O(g) + 3H 2 O(l) 1.29 Cr 2 O H + + 6e 2Cr H 2 O(l) 1.33 Cl 2 (g) + 2e 2Cl PbO 2 (s) + 4H + + 2e Pb H 2 O(l) Au e Au(s) MnO 4 + 8H + + 5e Mn H 2 O(l) HClO(aq) + 2H + + 2e Cl 2 (g) + 2H 2 O(l) 1.63 HClO 2 (aq) + 2H + + 2e HClO(aq) + H 2 O(l) H 2 O 2 (aq) + 2H + + 2e 2H 2 O(l) S 2 O e 2SO O 3 (g) + 2H + + 2e O 2 (g) + H 2 O(l) 2.07 F 2 (g) + 2e 2F 2.87 F 2 (g) + 2H + + 2e 2HF(aq) 3.06 B. Alkaline Solution E o (V) Mg(OH) 2 (s) + 2e Mg(s) + 2OH Al(OH) 3 (s) + 3e Al(s) + 3OH 2.30 Zn(OH) 2 (s) + 2e Zn(s) + 2OH Fe(OH) 2 (s) + 2e Fe(s) + 2OH H 2 O(l) + 2e H 2 (g) + 2OH H 2 O(l) + 2e H 2 (g) + 2OH (ph = 7) 0.43 Cd(OH) 2 (s) + 2e Cd(s) + 2OH Ni(OH) 2 (s) + 2e Ni(s) + 2OH 0.72 Fe(OH) 3 (s) + e Fe(OH) 2 (s) + OH S(s) + 2e S Cu 2 O(s) + H 2 O(l) + 2e 2Cu(s) + 2OH CrO H 2 O(l) + 3e Cr(OH) 3 (s) + 5OH 0.13 MnO 2 (s) + 2H 2 O(l) + 2e Mn(OH) 2 (s) + 2OH 0.05 NO 3 + H 2 O(l) + 2e NO 2 + 2OH 0.01 HgO(s) + H 2 O(l) + 2e Hg(l) + 2OH PbO 2 (s) + H 2 O(l) + 2e PbO(s) + 2OH ClO 3 + H 2 O(l) + 2e ClO 2 + 2OH 0.33 ClO 4 + H 2 O(l) + 2e ClO 3 + 2OH 0.36 O 2 (g) + 2H 2 O(l) + 4e 4OH NiO 2 (s) + 2H 2 O(l) + 2e Ni(OH) 2 (s) + 2OH MnO 4 + 2H 2 O(l) + 3e MnO 2 (s) + 4OH BrO 3 + 3H 2 O(l) + 6e Br + 6OH 0.61 ClO + H 2 O(l) + 2e Cl + 2OH 0.89

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