CHM 171 EKSAMEN / EXAMINATION

Outeursreg voorbehou UNIVERSITEIT VAN PRETORIA UNIVERSITY OF PRETORIA DEPARTEMENT CHEMIE DEPARTMENT OF CHEMISTRY DATUM / DATE : 6 Junie/June 2003 TYD / TIME : 120 min PUNTE / MARKS : 0 CHM 171 EKSAMEN / EXAMINATION EKSAMINATORE / EXAMINERS: Prof CA Strydom Prof JF van Staden Prof S Lotz EKSTERNE EKSAMINATOR / EXTERNAL EXAMINER: Prof WJ Schoeman **************** VAN EN VOORLETTERS: SURNAME AND INITIALS:: -------------------------------------------------------------------------------------------- -- STUDENTENOMMER: GRAADKURSUS: STUDENT NUMBER : -------------------------------- DEGREE COURSE: ------------------------------ - HANDTEKENING / SIGNATURE : -------------------------------------------------------- Totaal / Total Punte / Marks Afdeling/Part A Vrae/Questions 1-25 2 punte elk marks each 50 Afdeling/Part B Vraag/Question 1 Instruksies / Instructions Vraag/Question 2 Vraag/Question 3 Vraag/Question 4 Vraag/Question 5 Totaal / Total 0 1. Beantwoord afdeling B in ink. Antwoorde in potlood sal nie nagesien word nie. Answer part B in ink. Answers in pencil will not be marked. 2. Geen Tipp-ex of soortgelyke vloeibare papiermiddels mag op die antwoordstel gebruik word nie. / Do not use Tipp-ex or any similar liquid paper product on your paper. 3. Voorsien inligting op veelvuldige keuseblad volledig. / Give all information required on multiple question sheet. 4. Aangeheg : Periodieke tabel en element elektronegatiwiteite. Attached : Periodic table and element electronegativities. 1

5. A = 6.022 x 23 mol -1 0 C / 273.15K 2

Afdeling A / Part A Totaal / Total 50 Veelvuldige keusevrae / Multiple choice questions Punte per vraag / Marks per question 2 Identifiseer die letter van keuse wat die stelling die beste voltooi of wat die antwoord verskaf. Kleur die ooreenstemmende nommer op jou veelvuldige keusevraagvorm met potlood in. / Identify the letter of the choice that best completes the statement or answers the question and colour the representative number on your multiple choice question sheet with a pencil. 1. Hierdie antwoord verteenwoordig nie n homogene mengsel nie / This answer does not represent a homogeneous mixture a. Na/Hg mixture / Na/Hg mixture b. Oplossing van NaCl in water / aqueous solution of NaCl c. Al 2 (SO 4 ) 3 (s) d. Petrol / gasoline e. Waterige oplossing met vaste AgCl / aqueous solution with solid AgCl. 2. Merk die korrekte formule vir die gegewe naam van die verbinding./match the correct formula for the given name of the compound. Ammoniumnitried / Ammonium nitride a. (NH 4 ) 3 N b. NH 4 NO 3 c. NH 3 NO 2 d. N 2 O 3 e. NH 4 NO 2 3. Kies n paar wat n sulfiet en hipobromiet ioon korrek voorstel. / Select the pair that represents a sulphite and a hypobromite ion. a. BrO 2!, S 2! b. SO 4 2!, BrO 4! c. SO 3 2!, BrO d. BrO 3!, SO 3 2! e. S 2!, BrO 4. Al die onderstaande formules is korrek, BEHALWE / All of the following formulas are correct EXCEPT a. BaH 2 b. KClO 3 c. Fe 2 O 3 d. MgNO 2 e. Al 2 (H 2 PO 4 ) 3 5. Die som van die aantal protone, die aantal elektrone en die aantal neutrone vir die isotoop 1 35 1 P 3- is / The sum of the protons, electrons and neutrons for the isotope 1 35 1 P 3- is a. 31 b. 49 c. 15 d. 46 e. 43 6. Jy kan n element identifiseer deur baie versigtig die digtheid (d) daarvan te bepaal. n Onbekende stuk metaal het n massa van 29.454 g, is 2.35 cm lank, 1.34 cm breed en 1.05 cm dik. Watter een van onderstaande is die element? / You can identify a metal by carefully determining its density (d). An unknown piece of metal, with mass 29.454 g, is 2.35 cm long, 1.34 cm wide, and 1.05 cm thick. which of the following is the element? a. Ni (d=8.91 g/cm 3 ) b. Ti (d=4.50 g/cm 3 ) c. Zn (d=7.14 g/cm 3 ) d. Pb (d=11.34 g/cm 3 ) e. Sn (d=7.23 g/cm 3 ) 7. Druk 4.0 mm uit in die standaard notasie met die korrekte aantal betekenisvolle syfers. / Express 4.0 mm in standard notation using the correct number of significant figures. a. 1.040 x!2 m b. 1.040 x!4 km c. 1.040 x 2 cm d. 1.04 x 2 mm e. 1.04 x 2 cm 3

8. n Beker bevat 32.00 cm 3 broom (Br 2 ). As die digtheid van broom 2.928 g/cm 3 by 25 C is, bereken die aantal atome broom in die monster./ A beaker contains 32.00 cm 3 bromine (Br 2 ). If the density of bromine is 2.928 g/cm 3 at 25 C, determine the number of bromine atoms in the sample. a. 1.927 x 25 atoms b. 7.062 x 23 atoms c. 5.642 x 25 atoms d. 3.531 x 23 atoms e. geeneen/none 9. Ongeveer hoeveel mol suurstof is daar in 24.48 g Nikkel(II)sulfaatpentahidraat? / Approximately how many moles of oxygen are there in 24.48 g of nickel(ii) sulfate pentahydrate? a. 0.6 b. 0.5 c. 0.9 d. 0.2 e. 0.4. Koper het twee stabiele isotope 63 Cu en 65 Cu met massas 62.939598 ame en 64.927793 ame onderskeidelik. Die berekende persentasie voorkoms van 63 Cu is naastenby / Copper has two stable isotopes, 63 Cu and 65 Cu with masses of 62.939598 amu and 64.927793 amu, respectively. The calculated percent abundance of 63 Cu is approximately a. 31% b. 45% c. 55% d. 61% e. 69% 11. Wat is die maksimum aantal orbitale in n = 3? / What is the maximum number of orbitals in n = 3? a. 1 b. 3 c. 4 d. 7` e. 9 f. Geeneen/none 12. Die volgende stelle kwantumgetalle is almal korrek, BEHALWE / All of the following sets of quantum numbers are allowed EXCEPT a. n = 6, R = 3, m R = -3 b. n = 2, R = 1, m R = 0 c. n = 5, R = 0, m R = -1 d. n = 4, R = 2, m R = +2 e. n = 1, R = 0, m R = 0 f. Geeneen / none 13. Wat is die elektronkonfigurasie van Pb 2+? / What is the electron configuration for Pb 2+? a. [Xe]5d 6s 2 b. [Xe]4f 14 5d 6s 2 c. [Xe]6s 2 d. [Xe]4f 14 5d e. [Xe]4f 14 6p 2 f. Geeneen/none 14. Wat is n moontlike stel kwantumgetalle vir die ongedeelde elektron in die orbitaal boksdiagram? / What is a possible set of quantum numbers for the unpaired electron in the orbital box diagram below? a. n = 3, R = 1, m R = -1, m s = +1/2 b. n = 4, R = 1, m R = -1, m s = +1/2 c. n = 3, R = 2, m R = -2, m s = +1/2 d. n = 3, R = 2, m R = -1, m s = -1/2 e. n = 4, R = 2, m R = 0, m s = +1/2 f. geeneen / none 4

15. Watter een van die volgende katione het twee ongedeelde elektrone? / Which of the following cations has two unpaired electrons? a. Ni 2+ b. Sn 2+ c. Pb 2+ d. V 2+ e. Ca 2+ 16. Rangskik die volgende atome in volgorde van groterwordende atoomstrale: S, F, K, Cl, en Na. Place the following atoms in order of increasing atomic radii: S, F, K, Cl, and Na. a. K < Na < S < F < Cl b. Na < K < F < S < Cl c. S < Cl < F < K < Na d. F < Na < S < Cl < K e. F < Cl < S < Na < K 17. Wat is die bindingsorde tussen stikstof en suurstof in die nitraat ioon, NO 3 G? / What is the bond order for a nitrogen-oxygen bond in nitrate ion, NO 3 G? a. 1 b. 4/3 c. 3/2 d. 2 e. 3 18. Die oksidasiegetal van die onderstreepte atoom in NH 3 is/the oxidation number of the underlined atom in NH 3 is a. +3 b. -3 c. -2 d. 0 e. +1 f. -1 19. Wat is die oksidasiegetal van elke atoom in K 2 Cr 2 O 7? / What is the oxidation number of each atom in K 2 Cr 2 O 7? a. K = +1, Cr = +6, O = -2 b. K = +1, Cr = +7, O = -2 c. K = +2, Cr = +6, O = +2 d. K = -1, Cr = -1, O = +2 e. K = +1, Cr = -1, O = 0 f. geeneen / none 20. Watter van die volgende elemente is n reduseermiddel? / Which of the following elements is a reducing agent? a. O 2 b. K c. N 2 d. F 2 e. Ne 21. Al die volgende reaksies is oksideer-reduseer reaksies BEHALWE / All of the following are oxidation-reduction reactions EXCEPT a. H 2 (g) + Cl 2 (g) 2 HCl(g) b. C 6 H 12 O 6 (s) 6 C(s) + 6 H 2 O(R) c. Ca(s) + 2 HBr(aq) CaBr 2 (aq) + H 2 (g) d. 2 NaBr(aq) + F 2 (g) 2 NaF(aq) + Br 2 (g) e. 2 H 2 O(l) 2 H 2 (g) + O 2 (g) 22. Wat is die waarde van die standaard vormingsentalpie vir enige element onder standaard toestande? / What is the value of the standard enthalpy of formation for any element under standard conditions? a. 273 J/mol b. 0.24 J/mol c. 4.18 J/mol d. 0 J/mol e. nie een nie/none 23. Die standaard toestand van n element of verbinding word bepaal by n druk van en n temperatuur van./ The standard state of an element or compound is determined at a pressure of and a temperature of. a. 760 atm, 0 C b. 1 mmhg, 273 C c. 760 atm, 0 K d. 1 atm, 298 K e. geeneen/none 5

24. Die spesifieke warmte kapasiteit van yster is 0.451 J/g K. Wat is die molêre warmte kapasiteit van yster? / The specific heat capacity of iron is 0.451 J/g K. What is the molar heat capacity of iron? a. 0.451 J/mol K b. 26.0 J/mol K c. 25.2 J/mol K d. 55.85 J/mol K e. geeneen/none 25. Vir n sekere proses is q = 25 kj en w = -15 kj. Watter gevolgtrekkings kan oor die proses gemaak word? / For a particular process q = 25 kj and w = -15 kj. What conclusions may be drawn for this process? a. )E = 40 kj b. )E = -40 kj c. Dit is n produk gunstige reaksie. / This is a product favored reaction. d. Arbeid word deur die sisteem op die omgewing gedoen. / Work is done by the system on the surroundings. e. Beide b en d is korrek. / Both answer b and d are correct. 6

Afdeling B / Part B Totaal / Total 50 Antwoord in pen (ink) / Answer in pen (ink) Vraag 1 / Question 1 Loodsulfied, PbS, kan in twee reaksiestappe na loodmetaal omgeskakel word : / Lead sulphide, PbS, can be converted to lead metal in two reaction steps : 1. 2 PbS(s) + 3 O 2 (g) ÿ 2 PbO(s) + 2 SO 2 (g) Persentasie opbrengs / Percentage yield = 65.00% 2. PbO(s) + C(s) ÿ Pb(R) + CO(g) Persentasie opbrengs / Percentage yield = 75.00% Bereken die massa lood wat gevorm word as met 15.00 kg loodsulfied begin word. n Oormaat suurstof en koolstof word bygevoeg. / Calculate the mass lead that formed if 15.00 kg lead sulfide is used. An excess of oxygen and carbon is added. 7

Vraag 2 / Question 2 12.76 g van n onsuiwer monster wat natriumkarbonaat (Na 2 CO 3 ) bevat, word opgelos en met water verdun na 500. cm 3. 25.00 cm 3 van hierdie oplossing word volledig gereageer met 26.75 cm 3 van n 0.26 mol/l soutsuuroplossing. Bereken die persentasie natriumkarbonaat in die onsuiwer monster. / 12.76 g of an impure sample of sodium carbonate (Na 2 CO 3 ) is dissolved in water to give a 500. cm 3 solution. 25.00 cm 3 of this solution reacts completely with 26.75 cm 3 of a 0.26 mol/l hydrochloric acid solution. Determine the percentage sodium carbonate in the impure sample. Na 2 CO 3 (aq) + 2 HCl(aq) ÿ 2 NaCl(aq) + CO 2 (g) + H 2 O(R) Vraag 3 / Question 3 8

Gee die Lewisstruktuur vir ClF 3. Dui al die elektrone aan. / Give the Lewis structure for ClF 3. Show all the electrons. [4] Gebruik die VSEPR teorie om die elektronpaargeometrie van ClF 3 te voorspel. / Use the VSEPR theory to determine the electron pair geometry of ClF 3. [1] Gee en skets die molekulêre geometrie van ClF 3 en dui die groottes van die hoeke tussen die bindings aan. / Give and sketch the molecular geometry of ClF 3 and indicate what the angles between the bonds are. [4] Dui die rigting van die netto dipoolmoment aan. / Indicate the direction of the nett dipole moment. [1] Vraag 4 / Question 4 9

1 Gegee die volgende reaksie: / For the following reaction: I 2 (s) + SO 3 2G (aq) ÿ SO 4 2G (aq) + I G (aq) + H + (aq) Gee al die oksidasiegetalle. / Give all the oxidation numbers. [2] Gee die reduksie halfreaksie. / Give the reduction half reaction: [1] Gee die oksidasie halfreaksie. / Give the oxidation half reaction: [1] Balanseer die halfreaksies. / Balance the half reactions. Reduksie halfreaksie: / Reduction half reaction: [1] Oksidasie halfreaksie: / Oxidation half reaction: [1] Gee die volledig gebalanseerde reaksievergelyking. / Give the complete balanced reaction equation. [4]

Vraag 5 / Question 5 As 11.5 g van n sekere metaal by 88.5 C by 26.8 g water by 20.2 C gevoeg word, styg die temperatuur na 24.3 C. C vir water = 4.184 J/g K. / If 11.5 g of a certain metal at 88.5 C is added to 26.8 g of water at 20.2 C, the temperature changes to 24.3 C. C of water = 4.184 J/g K. (a) Bereken q vir water/calculate q for water en/and [5] (b) C vir die metaal/c for the metal. [5] 11

Periodic table of the elements / Periodieke tabel van die elemente 1A 8A 1 H 1,0079 2A 3A 4A 5A 6A 7A 2 He 4,0026 3 Li 6,941 4 Be 9,0122 5 B,811 6 C 12,011 7 N 14,0067 8 O 15,9994 9 F 18,9984 Ne 20,1797 11 Na 22,9898 12 Mg 24,3050 3B 4B 5B 6B 7B 8B 1B 2B 13 Al 26,9815 14 Si 28,0855 15 P 30,9738 16 S 32,066 17 Cl 35,4527 18 Ar 39,948 19 K 39,0983 20 Ca 40,078 21 Sc 44,9559 22 Ti 47,88 23 V 50,9415 24 Cr 51,9961 25 Mn 54,9380 26 Fe 55,847 27 Co 58,9332 28 Ni 58,693 29 Cu 63,546 30 Zn 65,39 31 Ga 69,723 32 Ge 72,61 33 As 74,9216 34 Se 78,96 35 Br 79,904 36 Kr 83,80 37 Rb 85,4678 38 Sr 87,62 39 Y 88,9059 40 Zr 91,224 41 Nb 92,9064 42 Mo 95,94 43 Tc (98) 44 Ru 1,07 45 Rh 2,9055 46 Pd 6,42 47 Ag 7,8682 48 Cd 112,411 49 In 114,82 50 Sn 118,7 51 Sb 121,757 52 Te 127,60 53 I 126,9045 54 Xe 131,29 55 Cs 132,9054 56 Ba 137,327 57 La* 138,9055 72 Hf 178,49 73 Ta 180,9479 74 W 183,85 75 Re 186,207 76 Os 190,2 77 Ir 192,22 78 Pt 195,08 79 Au 196,9665 80 Hg 200,59 81 Tl 204,3833 82 Pb 207,2 83 Bi 208,9804 84 Po (209) 85 At (2) 86 Rn (222) 87 Fr (223) 88 Ra 226,0254 89 Ac** 227.0278 4 Rf (261) 5 Ha (262) 6 Sg (263) 7 Ns (262) 8 Hs (265) 9 Mt (266) 1 Discovered Nov 94 111 Discovered Dec 94 LANTHANIDES* 58 Ce 140,115 59 Pr 140,9076 60 Nd 144,24 61 Pm (145) 62 Sm 150,36 63 Eu 151,965 64 Gd 157,25 65 Tb 158,9253 66 Dy 162,50 67 Ho 164,9303 68 Er 167,26 69 Tm 168,9342 70 Yb 173,04 71 Lu 174,967 ACTINIDES** 90 Th 232,0381 91 Pa 231,0359 92 U 238,0289 93 Np 237,0482 94 Pu (244) 95 Am (243) 96 Cm (247) 97 Bk (247) 98 Cf (251) 99 Es (252) 0 Fm (257) 1 Md (258) 2 No (259) 3 Lr (260)