8. Relax and do well.

Transcription

1 EM Exam III John III. Gelder November 7, 2001 Name TA's Name Lab Section INSTRUTIONS: 1. This examination consists of a total of 9 different pages. The last three pages include a periodic table, some useful mathematical equations, a solubility table and a table of equilibrium constants. 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 TESE 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 3, 5, 6b and 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 Page 6 TOTAL SORES (23) (20) (30) (9) (16) (100)

2 EM 1515 EXAM III PAGE 2 (9) 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) I(aq) + RbO(aq) b) Na 2 S(aq) + Fe(NO 3 ) 3 (aq) c) 6 5 N 2 (aq) + N(aq) (8) 2. Write the ionic and net ionic chemical equations for 1a). 1a) Ionic equation: Net Ionic equation: 1b) Ionic equation: Net Ionic equation: (6) 3. Give the name or draw the Lewis structure for each of the following compounds. 4,5-dimethyl-2-hexyne 2,3-dimethyl-2-butene

3 EM 1515 EXAM III PAGE 3 (20) 4. When 2 (g) is mixed with O 2 (g) at 2000 K, the equilibrium is achieved according to the equation below, 2 (g) + O 2 (g) 2 O(g) + O(g) In one experiment, the following equilibrium concentrations were measured; [ 2 ] = M [O 2 ] = M [ 2 O] = [O] = M a) alculate the value of K c, the equilibrium constant for the reaction. b) In a different experiment, 0.75 mol 2 (g) is mixed with 0.75 mol of O 2 (g) in a 3.00 liter reaction vessel at 2000 K. alculate the equilibrium concentrations, in moles per liter of all species at this temperature.

4 EM 1515 EXAM III PAGE 4 (30) 5. alculate the p for each of the following solution; a) M Ba(O) 2 b) M 3 5 O 2 (propionic acid) c) M ( 3 ) 3 N

5 EM 1515 EXAM III PAGE 5 Short Answer: Parts a d are worth 4 points, part e is worth 6 points and part f is worth 9 points. (20) 6a. Identify the acid, base, conjugate acid and conjugate base in the following chemical equation, PO 2 4 (aq) O 2 (aq) 2 PO 4 (aq) O 2 (aq) b) K for the reaction in 6a above has a value of 290. Identify the stronger acid and base in the reaction. acid base c) The p of a 5.50 x 10-4 M lo 3 solution is about Is lo 3 a strong acid or a weak acid? Explain. d) Identify the chemical specie(s) in the highest concentration in 6c. (Note: excluding water.) e) Identify each of the following substances as an acid or a base and write a chemical equation that describes the acid or base character. i) ( 3 ) 2 N 2 + (aq) ii) 4 7 O 2 (aq)

6 EM 1515 EXAM III PAGE 6 f) Kp is 2.00 at a certain temperature for the reaction below 2NO(g) + O 2 (g) ä 2NO 2 (g) The reaction mixture initially contains 1 atm of each compound in the equation, and then is allowed to proceed towards equilibrium. i) Will the total pressure of the reaction system increase, decrease or stay the same? Explain. ii) Will P NO = P O 2 when equilibrium is established? Explain. iii) The reaction between NO(g) and O 2 (g) is exothermic. What will happen to the magnitude of K if the temperature of the reaction is increased? Explain

7 EM 1515 EXAM III PAGE IA Li IIA 4 Be Na Mg K a Rb Sr s Ba Fr (223) Ra IIIA IVA VA VIA VIIA B N O F 9 10 Ne IIIB IVB VB VIB VIIB VIII IB IIB Sc Ti V r Mn Fe o Ni u Zn Ga Ge As Se Br Kr Y Zr Nb Mo Tc Ru Rh Pd Ag d In Sn Sb Te I Xe (98) La Periodic Table of the Elements f Al Si P S l VIIIA 2 Ta W Re 75 Os Ir Pt Au g 80 Tl Pb Bi Po At Rn (209) (210) Ac Rf Db Sg Bh s Mt (261) (262) (263) (262) (265) (266) e Ar (222) K w = 1.0 x Lanthanides Actinides e Pr Nd Pm Sm Eu Gd Tb Dy o Er Tm Yb Lu (145) Th Pa U Np Pu Amm Bk f Es Fm Md No Lr (244) (243) (247) (247) (251) (252) (257) (258) (259) (260) Useful Information K p = K c (RT ) n p = log[ + ] p + po = 14 x 1,2 = b± b2 4ac 2a for ax 2 + bx + c = x R = L atm mol K = J mol K

8 EM 1515 EXAM III PAGE 8 E.1 DISSOIATION ONSTANTS FOR AIDS AT 25 Name Formula K a1 K a2 K a3 Acetic 2 3 O x 10 5 Ascorbic 6 7 O x 10 3 Arsenic 3 AsO x x x Arsenous 3 AsO x Benzoic 7 5 O x 10 5 Boric 3 BO x Butyric acid 4 7 O x 10 5 arbonic 2 O x x yanic NO 3.5 x 10 4 itric O x x x 10 7 Formic O x 10 4 ydroazoic N x 10 5 ydrocyanic N 4.9 x ydrofluoric F 7.2 x 10 4 ydrogen chromate ion ro x 10 7 ydrogen peroxide 2 O x ydrogen selenate ion SeO x 10 2 ydrogen sulfate ion SO x 10 2 ydrogen sulfide 2 S 5.7 x x ypobromous BrO 2.0 x 10 9 ypochlorous lo 3.0 x 10 8 ypoiodus IO 2.0 x Iodic IO x 10 1 Lactic 3 5 O x 10 4 Malonic O x x 10 6 Oxalic 2 2 O x x 10 5 Nitrous NO x 10 4 Phenol 6 5 O 1.3 x Phosphoric 3 PO x x x Paraperiodic 5 IO x x 10 9 Propionic 3 5 O x 10 5 Pyrophosphoric 4 P 2 O 3.0 x x 10 3 Selenous 2 SeO x x 10 9 Sulfuric 2 SO 4 strong acid 1.2 x 10 2 Sulfurous 2 SO x x 10 8 Tartaric O x x 10 5 E.2 DISSOIATION ONSTANTS FOR BASES AT 25 Name Formula K b Name Formula K b Ammonia N x 10 5 ydroxylamine ON x 10 8 Aniline 6 5 N x Methylamine 3 N x 10 4 Dimethylamine ( 3 ) 2 N 5.4 x 10 4 Ethylamine 2 5 N x 10 4 Trimethylamine ( 3 ) 3 N 6.4 x 10 5 ydrazine 2 NN x 10 6

9 EM 1515 EXAM III PAGE 9 Solubility Table Ion Solubility Exceptions NO 3 soluble none lo 4 soluble none l soluble except Ag +, g 2+ 2, *Pb 2+ I soluble except Ag +, g 2+ 2, Pb 2+ SO 2 4 soluble except a 2+, Ba 2+, Sr 2+, g 2+, Pb 2+, Ag + O 3 2 insoluble except Group IA and N 4 + PO 3 4 insoluble + except Group IA and N 4 - O insoluble except Group IA, *a 2+, Ba 2+, Sr 2+ S 2 insoluble except Group IA, IIA and N + 4 Na + soluble none N + 4 soluble none K + soluble none *slightly soluble