Download 8 Questions in Exam 3 - Organic Chemistry | CHEM 113 and more Exams Chemistry in PDF only on Docsity! CHEM113 Dr. Tossell December8,1998 Hou;r Exam 3 (odd # seats) Show your work and explain your answers. R = 8.314 J moHK' 1 (15 pt) 1. In exactly a week, lO.OOfigof radon'222 produces 2.82 |ig of polonium-218 by radioactive decay. What is the value for the rate constant in d" 1 . (15 pt) 2. Complete the following nuclear equations: (lOpts) 3. (lOpts) 4. (a) (b) (c) (d) (e) Which (a) (b) (c) (d) 183 T 0 -7-7 Ir + j e > 172Er-» 256 115 D . 100 Fm ^ 46 Pd member of each pair 209 . 83 Bl or 2Q Ca or 18 9 F or 23 i ft Ne or o A 138 v. a. + 54 Xe + 0 of nuclides is probably more stable? Explain your answers. 213 n . 83 til 20 Ca 19 9 F 23 XT 11 Na (e) 203, 81 From the table of standard reduction potentials choose, (a) an oxidizing agent that can oxidize Fe(s) to Fe2+ but not Cu(s) to Cu2+ (b) a reducing agent that can reduce C\2 to Cl' but not I;> to P. (15pts) 5. For the half-reaction Mn04- + 8H+ +5 Ag(s) -> Mn2+ + 5Ag+ +4H2O(^), E° = 0.71 V. (a) What is E when [H+] = 0.100 M and the concentrations of all other species remain at 1.00 M? (b) What is E when [MnCV] = 0.100 M and the concentrations of all other species remain at LOOM? (10 pts) 6. How many amperes are required to deposit 0.72 g of Cr from a solution that contains Cr3+ in 30.0 min? (15 pts) 7. For the cell Ag(s)l Ag+ (aq, sat'd AgBr)| I Ag+ (aq, 0.100 M)l Ag(s) the measured value of E is 0.305 V. (a) What is [Ag+] in saturated AgBr? (b) What is the value of Ksp for AgBr? (10 pts) 8. A solution containing an unknown number of metal ions is treated with dilute HCI; no precipitate forms. The pH is adjusted to about 1, and HiS is bubbled through. Again no precipitate forms. The pH of the solution is then adjusted to about 8. Again H^S is bubbled through. This time a precipitate forms. The filtrate from this solution is treated with (NH^HPCU. No precipitate forms. Which metal ions are possibly present? Which are definitely absent within the limits of these tests? Figure 17.19 Qualitative analysis scheme for separating cations into groups. Al s *. Fe 2 ~, Fc'*.Cc> 2 *, \r',Cr'~, 7.n 2 *,Mn'-' Ba 2 ',Ca 2 *, \l>r NV, K~, \H 4 ~ \il(i b A/ HCI Pi I't ![)]! aU 1 1 Group 1 -Insoluble chlorides: AgCl, Hg2 CI :,,PbCl 2 I1 Remaining < jt i' i^ P : ,.:p,-,u 1 Group 2 Acid-insoluble sulfidcs: CuS, Bi 2 Sj , CdS, PbS, HgS, As 2 Sj,Sb 2 S 5 , SnS 2 \<id 11 ,S, i '_' W 1 1C! Add iMI 4 l : S Pi I'k Iflll Jt (' pH h i \ and hvdroxidei: AKOKh, re(OH)-,. CrIOHh, ZnS, NiS, CoS, MnS Pu'i Ipll.lli- 1 Add i.\H 4 Ml, I Group 4 - Insoluble phosphate' Ba,iP0 4 ) : . Cj 3 iP()4 | 2 . \1S NH 4 PO, \lkah metal U)ns and \H 4 ' : Na", K*. NH4 *
