FINALE EKSAMEN / FINAL EXAMINATION

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1 epartement hemie / epartment of hemistry atum / ate: Tyd / Time: 120 min Punte / Marks: 100 ksaminatore: xaminers: Mrs.. otha Mr M.. Molefe r M. M. Nkwelo r L.. Pilcher Prof. W. J. Schoeman ksterne / xternal Prof. R. Vleggaar r L. van der Merwe MY 127 INL KSMN / INL XMINTION Van en Voorletters: Surname and Initials: Studentenommer: Student Number: andtekening: Signature: Vraag / Question Punte / Marks ksaminator / xaminer Veelvuldige Keusevrae Multiple hoice Questions 35 Totaal / Total 100 % Toepaslike inligting is aangeheg aan fdeling. lle antwoorde, (berekeninge, sketse, diagramme, ens.) moet in ink gegee word in hierdie afdeling. ntwoorde in potlood sal nagesien word, maar geen dispuut oor punte sal hanteer word nie. lle berekeninge moet volledig getoon word. lle selfone moet afgeskakel word. pplicable information is attached to Section. ll answers (calculations, sketches, diagrams, etc.) must be given in ink in this section. nswers in pencil will be marked, but no dispute over marks will be entertained. ll calculations must be shown in full. ll cellphones must be switched off. 1

2 Vraag 1 Konsentrasie-eenhede en Oplossings [10] 'n 2.45 mol.dm 3 oplossing van ribose ( 5 10 O 5 ) in water het 'n digtheid van 1.29 g.cm -3 by ereken die kookpunt van hierdie oplossing. [6] Question 1 Units of concentration and Solutions [10] 2.45 mol.dm -3 solution of ribose ( 5 10 O 5 ) in water has a density of 1.29 g.cm -3 at alculate the boiling point of this solution. [6] 1.2 ereken die dampdruk van hierdie oplossing. [4] 1.2 alculate the vapour pressure of this solution. [4] 2

3 Vraag 2 lektrochemie [12] esmelte aluminiumchloried word geëlektroliseer by 'n lektriese stroom van 3.45 vloei vir 3½ uur deur die sel. ie sel word by 24.0 V bedryf. 2.1 Skryf die oksidasie- en reduksie halfreaksies wat in hierdie sel sal plaasvind neer en bereken die waarde van sel van hierdie sel. [3] Question 2 lectrochemistry [12] Molten aluminium chloride is electrolysed at n electrical current of 3.45 flows through the cell for 3½ hours. The cell is operated at 24.0 V. 2.1 Write the oxidation and reduction halfreactions which will take place and calculate the value of cell for this cell. [3] 2.2 ereken die volume van die gas wat gevorm word. ie temperatuur van die gas is 500. en die druk is 720. mmg. [5] 2.2 alculate the volume of gas that will be produced. The temperature of the gas is 500. and the pressure is 720. mm g. [5] 3

4 2.3 ereken die elektrisiteitkoste om hierdie hoeveel-heid gas te produseer. Neem aan dat die koste van elektrisiteit 56 sent per kilowatt-uur is. [4] 2.3 alculate the electricity cost for producing this amount of gas. ssume the cost of electricity is 56 cent per kilowatt-hour.[4] 4

5 Vraag 3 / Question 3: enaming, / Nomenclature [12] 3.1 enaam die volgende verbindings volgens IUP-reëls. Name the following compounds according to IUP rules. O N 2 Naam: (2) Name: OMe Naam:... (2) Name: 3.2 Teken n lynstruktuur met duidelike uitbeelding van die stereochemie van etiel (2R,3S)-3- chloro-2-hidroksibutanoaat. Plaas -1 aan die regterkant van die struktuur. raw a line structure clearly showing the stereochemistry of ethyl (2R,3S)- 3-chloro-2- hydroxybutanoate. Place -1 on the right-hand side of the line structure. (4) 3.3 ebruik die ahn-ingold-prelog sisteem om die geometrie van die gegewe verbinding te bepaal. Toon die atome en atoomgetalle wanneer jy een binding op n slag vanaf die - dubbelbinding beweeg. Wys ook die relatiewe prioriteite van die groepe. rei die gegewe templaat uit Indien nodig. Use the ahn-ingold-prelog system to determine the geometry of the given compound. Show atoms and atomic numbers as you proceed from the - double bond one bond at a time. lso show the relative priorities of the groups. xpand the given template as needed. (4) O r O 5

6 eometrie / eometry :.. Vraag 4 / Question 4: Teorie en Meganismes / Theory and Mechanisms [10] Skakel die gegewe Newmanprojeksie om na n lynstruktuur. ui die bindings in drie dimensies aan. onvert the given Newman projection to a line structure. Show the bonds in three dimensions. (2) Kyk langs die 2-3 binding van die volgende verbinding af en teken die mees-stabiele konformasies. Maak gebruik van die gegewe Newmanprojeksie templaat. raw the most stable conformations of the following molecule viewed along the 2-3 bond using the Newman projection templates provided. (2) 6

7 4.2.1 ebruik meganistiese pyltjies om die volgende omskakeling te verduidelik. Propose mechanistic arrows to explain the following transformation. (2) In die reaksie van n onsimmetriese alkeen met waterige suur kan twee moontlike karbokatione gevorm word. Verskaf die strukture van die karbokatione en merk hulle as primêr, sekondêr of tersiêr en dui aan watter vorm die waarskynlikste. In the reaction of an unsymmetrical alkene with aqueous acid two possible carbocations can form. ive the structures of the carbocations, label them as primary, secondary or tertiary and say which is most likely to form. (4) 7

8 Vraag 5 / Question 5: Koolhidrate / arbohydrates [9] 5.1 Skakel die ischerprojeksie van -idose om na n lynstruktuur. onvert the ischer projection of -idose to a line structure. (3) O O O O O 2 O -idose O 5.2 Teken die aworth-projeksie van α--idopiranose raw the aworth projection of α--idopyranose. (3) 5.3 Teken die mees-stabiele konformasie van α--idopiranose raw the most stable conformation of α--idopyranose. (3) 8

9 Vraag 6 / Question 6: Organiese Reaksies / Organic Reactions [12] 6.1 Verskaf die ontbrekende reagense en die lynstrukture van die uitgangstowwe en produkte in die volgende reaksies. Provide the missing reagents and line structures of substrates and products for the following reactions. (7) 6.2 Skryf reaksievergelykings vir die sintetiese omskakeling van 1-bromo-1-metielsiklopentaan na 1,2-dibromo-1-metielsiklopentaan. lke reaksiestap moet deur n volledige vergelyking voorgestel word waarin uitgangstof, reagense en organiese produkte aangetoon word. Meganismes word nie vereis nie.toon stereochemie aan waar toepaslik Write reaction equations for the synthetic conversion of 1-bromo-1-methylcyclopentane to 1,2- dibromo-1-methylcyclopentane. ach reaction step must be fully presented, including substrate, reagents and organic products. Mechanisms are not required. Show stereochemistry where applicable. (5) 9

10 UNIVRSITIT VN PRTORI UNIVRSITY O PRTORI PRTMNT MI PRTMNT O MISTRY MY 127 INL KSMN / INL XMINTION LIN : VLVOUI KUSVR STION : MULTIPL OI QUSTIONS 16 November eantwoord die volgende vrae op die rekenaar- antwoordblad. 2. ebruik slegs kant 2 van die antwoordblad. 3. Slegs een antwoord per vraag is toelaatbaar. 4. een punte word oorweeg vir onduidelike antwoorde nie. it is u verantwoordelikheid op te sorg dat die antwoordblad leesbaar is vir die optiese merkleser. lle instruksies is op die antwoordvorm aangebring. 5. ntwoorde word nie negatief nagesien nie. 1. nswer the following questions on the computer answer sheet. 2. Use only side 2 of the answer sheet. 3. Only one answer per question is allowed. 4. No marks are considered for unclear answers. It is your responsibility to ensure that the answer sheet is readable by the optical mark reader. ll instructions are provided on the answer sheet. 5. nswers are not marked negatively. Vraag 1 Maak asseblief seker dat u kant 2 van die antwoordblad gebruik. Merk opsie J van Vraag 1 op u rekenaarantwoordblad. it is slegs vir kontroledoeleindes. Vraag 2 [2] Watter een van die volgende stellings oor n perfekte (ideale) gas is korrek? ie kinetiese energie van die deeltjies is nul. ie gas het geen reaktiwiteit nie. een intermolekulêre kragte bestaan tussen die deeltjies nie. ie gas kondenseer by hoë druk. ie gasdeeltjies is mono-atomies. Nie een van bogenoemde nie. Question 1 Please make sure that you use side 2 of the answer sheet. Mark option J of Question 1 on your computer answer sheet. This is for control purposes only. Question 2 [2] Which one of the following statements of a perfect (ideal) gas is correct? The kinetic energy of the particles is zero. The gas has no reactivity. No intermolecular forces exist between the particles. The gas condenses under high pressure. The gas particles are mono-atomic. None of the above statements is correct. Vraag 3 [2] ie sterkste intermolekulêre kragte tussen sikloheksanoon-molekules is die volgende: Waterstofbinding. Permanente dipool - permanente dipool kragte eïnduseerde dipool - permanente dipool kragte eïnduseerde dipool- geïnduseerde dipool kragte ispersiekragte Nie een van bogenoemde nie. Question 3 [2] The strongest intermolecular forces between cyclohexanone molecules is the following: ydrogen bonding. Permanent dipole - permanent dipole forces. Induced dipole - permanent dipole forces. Induced dipole - induced dipole forces. ispersion forces. None of the above. 1

11 Vraag 4 [2] Watter een van die volgende stellings oor die kritiese temperatuur van n stof is korrek? it is die temperatuur van die trippelpunt by 1 atmosfeer druk. okant hierdie temperatuur kan die vloeistoffase nie bestaan nie. ie vloeistof sal altyd kook by hierdie temperatuur. ie vaste stof sal altyd smelt by hierdie temperatuur. ie vaste stof sal altyd sublimeer by hierdie temperatuur. Nie een van bogenoemde is korrek nie. Question 4 [2] Which one of the following statements of the critical temperature of a substance is correct? It is the temperature of the triple point at 1 atmosphere pressure. bove this temperature, the liquid phase cannot exist. The liquid will always boil at his temperature. The solid will always melt at his temperature. The solid will always sublime at his temperature. None of the above statements is correct. Vraag 5 [2] epaal die verdampingsentalpie van titaan(iv) chloried, met die volgende reaksie-entalpieë gegee: Ti(s) + 2l 2 (g) Til 4 (l) = kj Ti(s) + 2l 2 (g) Til 4 (g) = kj kj 41.0 kj kj kj kj Nie een van bogenoemde nie. Question 5 [2] etermine the enthalpy of evaporation of titanium(iv) chloride, given the enthalpies of reaction below. Ti(s) + 2l 2 (g) Til 4 (l) = kj Ti(s) + 2l 2 (g) Til 4 (g) = kj kj 41.0 kj kj kj kj None of the above. Vraag 6 [2] Watter van die volgende stellings is KORRK? 1. nergie word behou tydens enige chemiese proses. 2. In n spontane proses neem die entropie van slegs die sisteem toe. 3. Spontane veranderinge vind slegs plaas in die rigting wat lei tot ewewig. 4. ndotermiese reaksies is nooit spontaan nie. Slegs 1 Slegs1 en 2 Slegs 1, 2 en 3 Slegs 2, 3 en 4 Slegs 1 en 4 Slegs 1 en 3 Slegs 2 en 3 Slegs 3 en 4 I lmal is korrek. J Nie een is korrek nie. Question 6 [2] Which of the following statements is/are ORRT? 1. uring any chemical process, energy must be conserved. 2. In a spontaneous process, only the entropy of the system increases. 3. Spontaneous changes only occur in the direction that leads to equilibrium. 4. ndothermic reactions are never spontaneous. I J 1 only 1 and 2 only 1, 2 and 3 only 2, 3 and 4 only 1 and 4 only 1 and 3 only 2 and 3 only 3 and 4 only They are all correct. None of them are correct. 2

12 Vraag 7 [3] y watter temperature sal n reaksie spontaan wees as = 75.0 kj en S = 255 J/K? Question 7 [3] t what temperatures will a reaction be spontaneous if = 75.0 kj and S = 255 J/K? Temperature tussen 75.0 K en 255 K Temperatures between 75.0 K and 255 K lle temperature onder 180 K ll temperatures below 180 K lle temperature bo 180 K ll temperatures above 180 K lle temperature onder 294 K ll temperatures below 294 K lle temperature bo 294 K ll temperatures above 294 K ie reaksie is spontaan by alle temperature. The reaction will be spontaneous at any temperature ie reaksie is nooit spontaan nie. The reaction will never be spontaneous. Vrae 8, 9 en 10 verwys na die volgende orbitaaltekening: Questions 8, 9 and 10 refer to the following orbital drawing: Vraag 8 [1 ] ie molekulêre geometrie van atoom is: lineêr trigonaalvlakkig tetrahedraal trigonaalpiramidaal gebuig hoekig Question 8 [1] The molecular geometry of the atom labelled is: linear trigonal planar tetrahedral trigonal pyramidal bent angular Vraag 9 [1 ] ie hibridisasie van atoom is: sp sp 2 sp 3 s 2 p s 2p nie een van bogenoemde nie Question 9 [1] The hybridization of atom is:: sp sp 2 sp 3 s 2 p s 2p none of the above 3

13 Vraag 10 [2] ie molekulêre formule van die verbinding is: 5 N 2 O 5 NO NO 8 N 2 O 8 NO NO Question 10 [2] The molecular formula of the compound is: 5 N 2 O 5 NO NO 8 N 2 O 8 NO NO Vraag 11 [2 ] Watter een van die volgende verbindings is die mees stabiel? cis-1,2-dietielsikloheksaan trans-1,3-dietielsikloheksaan cis-1,4-dietielsikloheksaan trans-1,4-dietielsikloheksaan alle verbindings is ewe-stabiel Question 11 [2 ] Which one of the following compounds is the most stable? cis-1,2-diethylcyclohexane trans-1,3-diethylcyclohexane cis-1,4-diethylcyclohexane trans-1,4-diethylcyclohexane all compounds are equally stable Vraag 12 [2 ] Watter van die volgende verbindings is opties-aktief? Question 12 [2 ] Which of the following compounds are optically active? slegs I I only slegs II II only slegs III III only slegs IV IV only I en II I and II I en III I and III II en IV II and IV III en IV III and IV I lmal van I tot IV I ll of I to IV J Nie een van die bogenoemde antwoorde J None of the above answers Vraag 13 [2 ] Watter van die volgende verbindings het minder as 2 n stereoisomere? (n = aantal stereosentra) Question 13 [2 ] Which of the following compounds have fewer than 2 n stereoisomers? (n = no of stereocentres) 4

14 Vraag 14 [2 ] Wat is die stereochemiese verwantskap tussen die volgende twee verbindings? Question 14 [2 ] What is the stereochemical relationship between the following two compounds? Identies nomere nantiomere iastereomere Konstitusionele isomere Konformere Nie een van die bogenoemde Identical nomers nantiomers iastereomers onstitutional isomers onformers None of the above Vraag 15 [2 ] Wat is die stereochemiese verwantskap tussen die volgende twee verbindings? Question 15 [2 ] What is the stereochemical relationship between the following two compounds? Identies nomere nantiomere iastereomere Konstitusionele isomere Konformere Nie een van die bogenoemde Identical nomers nantiomers iastereomers onstitutional isomers onformers None of the above Vraag 16 [2 ] Watter stelling rakende benseen is verkeerd? benseen is n perfekte seshoek benseen se enkelbindings is 154 pm en dubbelbindings is 134 pm alle koolstowwe in benseen is sp 2 gehibridiseer alle koolstowwe in benseen het n 2p orbitaal met een elektron vir π - binding benseen is minder reaktief as alkene Question 16 [2 ] Which statement about benzene is false? benzene is a perfect hexagon benzene single bonds are 154 pm and double bonds are 134 pm. all carbons in benzene are sp 2 hybridised all carbons in benzene have a 2p orbital with one electron for π bonding benzene is less reactive than alkenes 5

15 Vraag 17 [2 ] Onder watter van die volgende kondisies sal benseen reageer om sikloheksaan te vorm?. Na in eter. 2, Pd-. 2, PtO 2. 2, Lindlar. 2 (136 atm), Pt. Nie een van die bogenoemde Question 17 [2 ] Under which of the following conditions will benzene react to form cyclohexane?. Na in ether. 2, Pd-. 2, PtO 2. 2, Lindlar. 2 (136 atm), Pt. None of the above Vraag 18 [2 ] ie produk van hierdie reaksie is n... Question 18 [2 ] The product of this reaction is a/an. asetaal acetal ester ester hemiasetaal hemiacetal hidraat hydrate een produk form No product forms Vraag 19 [2 ] ie beste reagens vir hierdie reaksie is: Question 19 [2 ] The best reagent system for carrying out this transformation is: i) Na 4 ; ii) 3 O + P, 2 l 2 2 SO 4, 2 O ro 3, 2 SO 4, 3 O + Nie een van bogenoemde i) Na 4 ; ii) 3 O + P, 2 l 2 2 SO 4, 2 O ro 3, 2 SO 4, 3 O + None of the above INS IN KSMNVRSTLL Slegs op Maandag 29 November :00 12:00 in die Orbital hemiegebou 3de vloer INSPTION O XM SRIPTS Only on Monday 29 November :00 12:00 in the Orbital hemistry building 3 rd loor Moenie enige sakke of skryfbehoeftes saambring nie, aangesien dit nie in die lokaal toegelaat gaan word nie. o not bring any bags or stationery as you will have to leave them outside the venue. 6

16 Standard Reduction Potentials in queous, cidic or asic Solution at 25 * Standaard Reduksie Potensiale in Waterige, Suur- of asiese Oplossing by 25 *... Reduction alf-reaction / Reduksie alf-reaksie (V) 2 (g) + 2 e 2 (aq) O2 (aq) + 2 3O + (aq) + 2 e 4 2O (l) PbO2 (s) + SO 2 4 (aq) + 4 3O + (aq) + 2 e PbSO4 (s) + 6 2O (l) MnO 4 (aq) + 8 3O + (aq) + 5 e Mn 2+ (aq) O (l) u 3+ (aq) + 3 e u (s) l2 (g) + 2 e 2 l (aq) r2o7 2- (aq) O + (aq) + 6 e 2 r 3+ (aq) O (l) O2 (g) + 4 3O + (aq) + 4 e 6 2O (l) r2 (l) + 2 e 2 r (aq) NO 3 (aq) + 4 3O + (aq) + 3 e NO (g) + 6 2O (l) Ol (aq) + 2O (l) + 2 e l (aq) + 2 O (aq) g 2+ (aq) + 2 e g (l) g + (aq) + e g (s) g + (aq) + 2 e 2 g (l) e 3+ (aq) + e e 2+ (aq) I2 (s) + 2 e 2 I (aq) O2 (g) + 2 2O (l) + 4 e 4 O (aq) u 2+ (aq) + 2 e u (s) Sn 4+ (aq) + 2 e Sn 2+ (aq) (aq) + 2 e 2 (g) O + (aq) + 2 e 2 (g) + 2 2O (l) 0.00 Pb 2+ (aq) + 2 e Pb (s) Sn 2+ (aq) + 2 e Sn (s) Ni 2+ (aq) + 2 e Ni (s) V 3+ (aq) + e V 2+ (aq) PbSO4 (s) + 2 e Pb (s) + SO 2 4 (aq) d 2+ (aq) + 2 e d (s) e 2+ (aq) + 2 e e (s) Zn 2+ (aq) + 2 e Zn (s) O (l) + 2 e 2 (g) + 2 O (aq) [Zn(N)4] 2- (aq) + 2 e Zn (s) + 4 N (aq) l 3+ (aq) + 3 e l (s) Mg 2+ (aq) + 2 e Mg (s) Na + (aq) + e Na (s) K + (aq) + e K (s) Li + (aq) + e Li (s) *In volts (V) versus the standard hydrogen electrode / In volts (V) teen die standaard waterstofelektrode 7

17 Li Na K Rb s r e Mg a Sr a Ra Sc Y La c Ti Zr f Rf V Nb Ta b I PRIOIK TL VN I LMNT T PRIOI TL O T LMNTS 24 r Mo W Sg Mn Tc Re h e Ru Os s o Rh Ir Mt Ni Pd Pt u g u Zn d g l a In Tl Si e Sn Pb N P s Sb i O S Se Te Po l r I t e Ne r Kr Xe Rn e Th Pr Pa Nd U Pm Np Sm Pu u m d m Tb k y f o s r m Tm Md Yb No Lu Lr Vergelykings / quations P tot = n tot(rt/v) rxn = Σm f (prod) - Σn f (react) = n.. P tot = P 1 + P 2 + P P a=χ a(p tot) S sys = ΣmS sys (prod) ΣnS sys (react) = Σm f (prod) Σn f (react) = R.T. ln Q n. P solv=χ solvp solv π = MRT S univ = S sys + S surr S surr = q surr = - sys = log Q n (25 ) S g=k P g T= K m i = q + w q =.m. T of/or q = s. m. T W max = n T T = T S = + RT ln Q = RT ln K log K eq = n ln Q or K = log Q or K (25 ) Konstante / onstants R = L.atm.mol 1.K 1 = J.mol 1.K 1 = kpa.dm 3.mol -1.K -1 = mm g.l.mol -1.K -1 0 = K N = x mol -1 = x 10 4.mol 1 of/or J.V 1.mol 1 e = x ( 2O(l)) = J.g 1.K 1 = s ( 2O(l)) K b ( 2 O) = o /m P vap (water, 25 o ) = 23.8 mm g 1 amu = x g onversion actors 1 L = 10 3 m 3 = 1 dm 3 1 bar = x 10 5 Pa 1 = 1 mp. 1 sec 1 J = cal = 1 Pa m 3 = 1 m 2 kg s 2 = 1 V = 1 Watt.1 sec 1 atm = x 10 5 N m 2 = x 10 5 Pa = 760 mmg = 760 torr unksionele groepe in prioriteitsvolgorde / Priority order of functional groups karboksielsuur > ester > aldehied > ketoon > alkohol > tiol > amien > alkeen > alkyn > alkaan >> eter; halied carboxylic acid > ester > aldehyde > ketone > alcohol > thiol > amine > alkene > alkyne > alkane >> ether; halide 8

CMY 127 EKSAMEN / EXAMINATION

DEPARTEMENT CHEMIE DEPARTMENT OF CHEMISTRY CMY 127 EKSAMEN / EXAMINATION DATUM / DATE: 20 November 2012 EKSAMINATORE: Prof. WJ Schoeman EXAMINERS: Prof. M Potgieter TYD / TIME: 3 ure / hours Prof. R Vleggaar