CHM 172 SEMESTER TEST 1 / SEMESTERTOETS 1. Student number Studentenommer. Signature Handtekening. Marks / Punte. Question 1 / Vraag 1 8

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UNIVERSITY F PRETRIA UNIVERSITEIT VAN PRETRIA DEPARTEMENT F CHEMISTRY DEPARTMENT CHEMIE Fakulteit Natuur- en Landbouwetenskappe DATE / DATUM: 3 August 014 TIME / TYD: 150 min MARKS / PUNTE: 76 CHM 17

1 UNIVERSITY F PRETRIA UNIVERSITEIT VAN PRETRIA DEPARTEMENT F CHEMISTRY DEPARTMENT CHEMIE Fakulteit Natuur- en Landbouwetenskappe DATE / DATUM: 3 August 014 TIME / TYD: 150 min MARKS / PUNTE: 76 CHM 17 SEMESTER TEST 1 / SEMESTERTETS 1 Surname Van Initials Voorletters Memorandum Student number Studentenommer Signature Handtekening Marks / Punte Question 1 / Vraag 1 8 Examiner / Eksaminator Section A Afdeling A Question / Vraag 13 Question 3 / Vraag 3 8 Question 4 / Vraag 4 13 Section A 4 Section B Afdeling B 34 Total / Totaal 76 Instructions Answer all questions in ink on the white paper and pencil on the pink multiple choice paper. Do not use Tipp-Ex or any similar liquid paper product on your paper. Answers that should not be marked must be clearly indicated. All cell phones must be switched off. Use the data on the Information page for your calculations, not the data on calculators. Instruksies Beantwoord alle vrae in ink op die witpapier en potlood op die pink veelvuldige keuse papier. Geen Tipp-Ex of soortgelyke vloeibare papiermiddels mag op die antwoordstel gebruik word nie. Antwoorde wat nie nagesien moet word nie, moet duidelik doodgetrek word. Alle selfone moet afgeskakel wees. Gebruik data op die Inligtingsblad vir jou berekeninge, nie niee die 1/11

2 Section A : Show all calculations Afdeling A: / Toon alle berekeninge Question 1a 3 Vraag 1a A cation is formed when electrons are removed from an atom. Calculate the ionisation energy, in kj/mol, for the one electron beryllium cation, Be 3+. n Katioon vorm indien n elektron van n atom verwyder word. Bereken die ionisasie-energie, in kj/mol, vir die een-elektron berylliumkatioon, Be 3+. Electron has to be removed from n = 1 to n = E = RhcZ 1 1 n fin n init = ( m 1 )( J s)( m s 1 )(4 ) = J( 1) = J (per electron) kj/e e /mol = kj/mol Question 1b 3 Vraag 1b Calculate the wavelength of the electromagnetic radiation required to excite an electron from the nd energy level to the 5 th energy level, for this beryllium cation. Bereken die golflengte van die elektromagnetiese straling benodig om n elektron op te wek van die de energievlak tot die 5 de energievlak, vir hierdie berylliumkatioon. E = RhcZ 1 1 n fin n init = ( m 1 )( J s)( m s 1 )(4 ) = J( 0.10) = J λ = hc E = ( J s)( m s 1 ) = m J University of Pretoria /11

3 Question 1c Vraag 1c Assume a sample of this beryllium cation is radiated with a stream of photons with the required energy to repeatedly excite the cation as described in 1b. How many spectral lines would you expect as the electrons return to the ground state? Use a diagram to clearly illustrate how you determined your answer. Neem aan dat hierdie berylliumkatioon bestraal word met n stroom fotone met die vereiste energie om die katioon herhaaldelik op te wek soos beskryf in 1b. Hoeveel lyne verwag jy in die lynspektrum as die elektrone terugkeer na die grondtoestand? Toon duidelik met behulp van n diagram hoe jy die antwoord bepaal het. ne-electron system: All transitions between main energy levels of n=1,, 3, 4 and 5: 10 lines in the spectrum. n=5 n=4 n=3 n= n=1 Question a 4 Vraag a A pycnometer is a glass apparatus used for accurately determining the density of a liquid. When dry and empty, a certain pycnometer had a mass of g. When filled with distilled water at 5.0 o C, it has a mass of oz. When filled with chloroform, the apparatus weighed oz. At 5.0 o C, the density of water is g/ml. (i) What is the volume of the pycnometer? n Piknometer is a glasapparaat wat gebruik word om die digtheid van n vloeistof akkuraat te bepaal. n Droë en leë piknometer het n massa van g. Wanneer dit met gedistilleerde water by 5.0 gevul is, het dit n massa van ons. Wanneer die met chloroform gevul word weeg die apparaat ons. By 5.0 is die digtheid van water g/ml. (i) Wat is die volume van die piknometer? g Mass of water: ( oz ) g = 9.58 g 16 oz Volume of picnometer: V = m ρ = 9.58 g = ml g/ml 4 sf 3 dp (ii) What is the density (in g/cm 3 ) of chloroform at 5.0? (ii) Wat is die digtheid (in g/cm 3 ) van chloroform by 5.0? Mass of chloroform: ( oz ρ = m g = V cm3 = g/cm g 16 oz ) g = g 4 sf University of Pretoria 3/11

4 Question b 4 Vraag b The two isotopes of an element Q are 97 Q (3.38% abundance) and 94 Q (76.6% abundance). 97 Q is 8.08 times heavier than 1 C and 94 Q is times heavier than 1 C. What is the average relative atomic mass of the element Q? 97 Q: = u 94 Q: = u Avg atomic mass = Σ(fraction)(isotope mass) = (0.338)( u) + (0.766)(93.996) =.6749 u u = u u Die twee isotope van n element Q is 97 Q (3.38% voorkoms) en 94 Q (76.6% voorkoms). 97 Q is 8.08 maal swaarder as 1 C en 94 Q is maal swaarder as 1 C. Wat is die gemiddelde relatiewe atoommassa van element Q? 4 sf Question c 5 Vraag c In the technique known as photo-electron spectroscopy (PES), ultraviolet radiation ejects electrons from the valence shell of an atom or molecule. The energy of the incoming ultraviolet radiation is known and the kinetic energy of the outgoing electron is measured. This allows for the calculation of the ionisation energy, using hυ = IE + 1 m ev. Use this relationship to calculate the ionisation energy of a rubidium atom, in kj/mol, given that incoming radiation of wavelength 58.4 nm produces electrons with a velocity of 450 km/s. In die tegniek bekend as foto-elektronspektrokopie (FES), skiet ultravioletstraling elektrone uit die valensvlak van n atoom of molekule. Die energie van die invallende ultravioletstraling is bekend en die kinetiese energie van die uitgaande elektron word gemeet. Dit lei daartoe dat die ionisasie-energie bereken kan word, deur gebruik te maak van hυ = IE + 1 m ev. Gebruik hierdie verwantskap om die ionisasie-energie van n rubidiumatoom in kj/mol te bereken, gegee dat die inkomende straling met golflengte 58.4 nm, elektrone produseer met n snelheid van 450 km/s. hυ = IE + 1 m ev hc λ = IE + 1 m ev ( J s) m s m J = IE kg m s IE = J per electron J/e e/mol = J/mol = 40 kj/mol = IE + ( kg)( m/s) 3 sf University of Pretoria 4/11

5 Question 3a 4 Vraag 3a Give an energy diagram as well as the noble gas notation electron configuration for the Ni(II) ion 3d Gee die energiediagram asook die edelgasnotasie elektron-konfigurasie vir die Ni(II) ioon. 4s 3p May leave out the 4s orbital 3s p s 1s 8 Ni + : [Ar] 3d 8 Question 3b 4 Vraag 3b Give a full set of 4 quantum numbers for each unpaired electron in the orbital of highest subshell energy in the Ni(II) ion. Indicate which of the quantum numbers will give the shape of the region in space with the highest probability of finding the electron and draw this region of highest probability for each of the unpaired electrons. Gee ŉ volledige stel van 4 kwantumgetalle vir elke ongepaarde elektron in die orbitaal met die grootste subskilenergie in die Ni(II)-ioon. Toon aan watter van die kwantumgetalle sal die vorm van die ruimte met die hoogste waarskynlikheid om die elektron te vind aandui en teken hierdie ruimte van hoogste waarskynlikheid vir elk van die ongepaarde elektrone. n l m l m s 1 st unpaired e 3 +½ nd unpaired e 3 1 +½ Also accept m l values of 0, 1 and + but the values must be different for the two electrons Accept +½ and ½ for m s, but the spin must be in the same direction for the two electrons. l = indicates that it is a d-orbital; m l indicates the region in space with highest probability; any two of the d-orbitals z y z x z x -y z z z y x y x y x xy yz xz University of Pretoria 5/11

Question 4.1 3 Vraag 4.1 Draw the Lewis dot structure of ICl. Use different symbols for the valance electrons of the central atom (e.g. crosses) and terminal atoms (e.g. dots). Show all lone pairs.

6 Question Vraag 4.1 Draw the Lewis dot structure of ICl. Use different symbols for the valance electrons of the central atom (e.g. crosses) and terminal atoms (e.g. dots). Show all lone pairs. NB! Do not use lines (dashes) for bonds. Your drawing must clearly show the positions of the electrons. Teken die Lewis kolstruktuur van ICl. Gebruik verskillende simbole vir die valenselektrone van die sentrale atoom (bv. kruisies) en terminale atome (bv. kolletjies). Wys alle alleenpare. NB! Moet nie strepies gebruik vir bindings nie. Jou skets moet die posisies van die elektrone duidelik wys. Extra e not on [ 1] ne not double bonded [ 1] No brackets [ 1] Question 4. Vraag Draw the most likely Lewis line structures for S 3 and S 3 - in order to compare their molecular geometries. Show all lone pairs Indicate the sizes of the bond angles. Draw the line structure in 3D if applicable, using lines, wedges and broken lines for bonds. S 3 Teken die mees waarskynlike Lewis lynstrukture vir S 3 en S 3 - om sodoende hulle molekulêre geometrië te vergelyk. Wys alle alleenpare Dui die groottes van die bindingshoeke aan. Teken die struktuur in 3D indien van toepassing. Gebruik dan lyntjies, wiggies en gebroke lyne vir bindings. S 10 o S 3 - S - <109.5 o Comment: Most likely structures will have the best charge distribution check with formal charges. University of Pretoria 6/11

7 Name the electron pair geometry. Benoem die elektronpaar geometrie. (a) S 3 (b) S 3 - Trigonal planar Tetrahedral Name the molecular geometry. Benoem die molekulêre geometrie. (a) S 3 (b) S 3 - Trigonal planar Trigonal pyramidal Indicate the bond dipole moments with appropriate arrows in your drawing of S 3 in 4..1.Then answer the next question: Is S 3 polar or non-polar? Briefly motivate your answer. Dui die bindings dipoolmomente aan met gepaste pyltjies in jou skets van S 3 in 4..1 en antwoord dan die volgende vraag: Is S 3 polêr of nie-polêr? Motiveer jou antwoord kortliks. Non-polar. The three individual bond dipole moments have a resultant molecular dipole moment of zero. Section B: Multiple choice. Show all calculations Instructions: Answer all the questions on SIDE of the answer sheet provided. Make sure you fill in your name, student number etc. in the space provided. Mark only one oval per question. Use a pencil only. Submit both your completed answer sheet and the question paper. Afdeling B: Veelvuldige keuse. Toon alle berekening Instruksies: Beantwoord al die vrae op KANT van die antwoordblad. Maak seker dat u u naam, studente nommer ens. in die spasie voorsien invul. Merk net een keuse per vraag. Gebruik alleenlik n potlood. Handig beide u voltooide antwoordblad en die vraestel in. Question 1 Vraag 1 Mark option H of Question 1 on your computer answer sheet. This is for control purposes only and ensures that you use SIDE of the answer sheet. Merk opsie H van Vraag 1 op u rekenaarantwoordblad. Dit is slegs vir kontroledoeleindes en vereker dat u KANT van die antwoordblad gebruik. Question Vraag Some chemical reactions can be initiated by light that carries energy of 375 kj/mol. What is the longest wavelength of light, in nm, that can deliver 375 kj/mol A 375 E 3189 B 319 F 31.3 C 530 G None of the these/ D 597 Geeneen van hierdie Sommige chemise reaksies kan deur lig met energie van 375 kj/mol begin word. Wat is die langste golflengte van lig, in nm, wat 375 kj/mol kan aflewer? J 1 mol 1 mol photon = J λ = hc E = m = 319 nm University of Pretoria 7/11

8 Question 3 3 Vraag 3 The velocity of an electron that is emitted from a metallic surface by a photon in the photoelectric effect is 00 km/s. What is the wavelength of the electron? Die snelheid van n elektron wat deur n foton uit n metaaloppervlakte geskiet word is 00 km/s. Wat is die golflengte van die elektron? A m E m B m F m C m G None of these/ D m Geeneen van hierdie λ = h mv = h e m m = m s Question 4 Vraag 4 The number of orbitals with the quantum numbers n = 4, l = and m l = 0 is Die aantal orbitale met die kwantumgetalle n = 4, l = and m l = 0 is A 1 E 5 B F 6 C 3 G 7 D 4 1 there is only one d-orbital in the 4 th energy level with an m l value of 0 Question 5 Vraag 5 The number of valence electrons in the outermost p subshell of a selenium atom is A 1 E 5 B F 6 C 3 G None of these / Geeneen van hierdie D 4 Die aantal valenselektrone in die buitenste p subskil van die seleniumatoom is 4 th element in p-block 4 valence p-electrons Se: [Ar] 4s 3d 10 4p 4 Question 6 Vraag 6 The number of unpaired electrons in a Cu + ion is Die getal ongepaarde elektrone in die Cu + ioon is A 0 E 4 B 1 F 5 Cu: [Ar] 4s 1 3d 10 C G 6 Cu + : [Ar] 4s 0 3d 10 D 3 H None of these / Geeneen van hierdie Question 7 Vraag 7 The maximum number of electrons with quantum numbers n = 3 and l = 1 is Die maksimum aantal elektrone met kwantumgetalle n = 3 en l = 1 is A 1 E 5 B F 6 C 3 G None/ Geeneen p-orbitals in 3 rd energy level 6 e D 4 Question 8 Vraag 8 The name of the compound with chemical formula HN is Die naam van die verbinding met chemiese formule HN is A hydrogen dioxynitrite B nitric acid C nitrous acid D hyponitrous acid E hydrogen dioxynitrate F hyponitric acid G None of the above A waterstofdioksinitriet B salpetersuur C salpetrigsuur D hiposalpetrigsuur E waterstofdioksinitraat F hiposalpetersuur G Nie een van bogenoemde nie University of Pretoria 8/11

9 Question 9 Vraag 9 The name of the compound with chemical formula Fe(Cl ) is A iron(i) perchlorate B iron(i) tetraoxy chloride C iron(i) chlorate D iron(ii) hypochlorite E iron(ii) chlorite F iron(ii) perchlorate G iron(i) perchlorite H None of the above. Die naam van die verbinding met chemiese formule Fe(Cl ) is A yster(i)perchloraat B yster(i)tetra-oksichloried C yster(i)chloraat D yster(ii)hipochloriet E yster(ii)chloriet F yster(ii)perchloraat G yster(i)perchloriet H Nie een van bogenoemde nie. Question 10 Vraag 10 Which ion has the largest radius? Watter van die volgende ione het die grootste radius? A D F B S E Ca + C Br F Se H F Question 11 Vraag 11 Which atom has the lowest second ionization energy? Watter atoom het die laagste tweede ionisasie-energie? A Ar D Cl Mg Cl Ar B K E Mg K Ca C Ca F Rb Rb Which atom has the lowest electron affinity (electron attachment enthalpy)? A Ba D Cl B Sr E Mg C Cs F Rb S Se Question 1 Vraag 1 Br Watter atoom het die laagste elektronaffiniteit (elektonwinsentalpie)? Question 13 Vraag 13 The chemical formula for sodium oxalate is Die chemiese formule van natriumoksalaat is A Na 3 E Na C 4 B Na 3 F NaCH C Na G None of the above / Nie een van bogenoemde nie D NaNC Question 14 Vraag 14 The chemical formula for iron(iii) sulphate is Die chemiese formule van yster(iii)sulfaat is A Fe(S 4 ) 3 E Fe S 3 B Fe 3 S 4 F FeS 3 C Fe (S 4 ) 3 G None of the above / Nie een van bogenoemde nie D Fe 3 S 3 Rb Cs Mg Sr Ba Cl University of Pretoria 9/11

Question 15 Vraag 15 What are the formal charges on C, N and S in the Wat is die formele ladings op C, N en S in die structure of methylene(thioxo)ammonium below?

10 Question 15 Vraag 15 What are the formal charges on C, N and S in the Wat is die formele ladings op C, N en S in die structure of methylene(thioxo)ammonium below? onderstaande struktuur van metileen(tiokso)ammoniak? A C = 0 N = 0 S = 0 Structure/Struktuur B C = 0 N = +1 S = C C = 1 N = +1 S = 1 D C = 0 N = +1 S = 0 E C = 0 N = 0 S = +1 F C = +1 N = 0 S = 0 G C = 0 N = 0 S = +1 H C = 0 N = 1 S = + I None of the above / Geen van bogenoemde Question 16 3 Vraag 16 Which of the following structures form part of the resonance system for Br 4? [Hint: make use of formal charges] Watter van die volgende strukture vorm deel van die resonans-sisteem vir Br 4? [Wenk: maak gebruik van formele ladings] A B C D E F G All the structures / Al die strukture None of the structures / Geen van die strukture A, B, D and/en E A and/en E nly/slegs C nly/slegs B None of the above options / Geen van bogenoemde opsies Question 17 Vraag 17 The number of bonding electron pairs around chlorine in the most likely structure of the chlorate anion is A 0 B 1 C D 3 E 4 F 5 G 6 H 7 Die aantal bindings-elektronpare rondom chloor in die mees waarskynlikste struktuur van die chloraat-anioon, is Draw the structure here /Teken die struktuur hier University of Pretoria 10/11

11 INLIGTINGSBLAD / INFRMATIN PAGE DIE PERIDIEKE TABEL VAN ELEMENTE THE PERIDIC TABLE F THE ELEMENTS 1 Key / Sleutel 74 Atomic number / Atoomgetal H W Element symbol / Element simbool He Relative Atomic mass / Relatiewe atoommassa (u) Electronegativity / Elektronegatiwiteit Li Be B C N F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe (98) Cs Ba La Hf Ta W Re s Ir Pt Au Hg Tl Pb Bi Po At Rn (09) (10) () Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Cn Fl Lv (3) (61) (6) (63) (6) (65) (66) (71) (7) (85) Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu (145) Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr (44) (43) (47) (47) (51) (5) (57) (58) (59) (60) Vergelykings / Equations E = hv E n = Rhc Z n E = RhcZ 1 1 n fin λ = h mv ph = log [H 3 + ] ph + ph = 14 ΔU = q + w q = mcδt n init r H o = nδ f H o (prod) mδ f H o (react) r S o = ns o (prod) ms o (react) r G o = nδ f G o (prod) mδ f G o (react) o ΔS univ o = ΔS sys o + ΔS surr o S surr = q surr T = H sys T Δ r G o = Δ r H o TΔ r S o Δ r G = Δ r G o + RTlnQ o w max = nfe Δ r G o = nfe o Δ r G o = RTlnK E = E o RT nf lnq E = E o logq (5 C) n logk eq = neo (5 C) lnk =.303logK lnq =.303logQ Konstante / Constants h = J s R = m 1 c = m s 1 N A = F = C mol 1 of/or J V 1 mol 1 e = C M e = kg 0 C = K C (H (l)) = J g 1 K 1 C (H (s)) =.06 J g 1 K 1 C (H (g)) = 1.9 J g 1 K 1 fus H o (water) = 6.01 kj mol 1 vap H o (water) = kj mol 1 Gas constant / gaskonstante, R: = L atm mol 1 K 1 = J mol 1 K 1 = kpa L mol -1 K -1 = 6.36 mm Hg L mol -1 K -1 msettingsfaktore / Conversion Factors 1 u = g 1 L = 10 3 m 3 = 1 dm 3 1 bar = x 10 5 Pa 1 C = 1 Amp 1 sec 1 inch =.54 cm 1 ft = 1 inches 1 yard = 3 feet 1 lb = 16 oz = g 1 duim =.54 cm 1 voet = 1 duim 1 tree = 3 voet 1 pond = 16 ons = g 1 cal = J 1 Å = m 1 J = cal = 1 Pa m 3 = 1 m kg s = 1 V C = 1 Watt 1 sec 1 atm = x 10 5 N m = x 10 5 Pa = 760 mm Hg = 760 torr University of Pretoria 11/11

CHEM 172 EXAMINATION 1. January 15, 2009

CHEM 172 EXAMINATION 1. January 15, 2009 CHEM 17 EXAMINATION 1 January 15, 009 Dr. Kimberly M. Broekemeier NAME: Circle lecture time: 9:00 11:00 Constants: c = 3.00 X 10 8 m/s h = 6.63 X 10-34 J x s J = kg x m /s Rydberg Constant = 1.096776 x