School of Chemistry
University of KwaZulu-Natal, Howard College Campus, Durban
June 2011 Examinations
CHEM261: APPLIED INORGANIC CHEMISTRY FOR CHEMICAL ENGINEERS
Duration: 2 hours
Total marks: 100
External Examiner:
Dr S. Singh
University of KwaZulu-Natal
Internal Examiner:
Dr V.O. Nyamori
IMPORTANT: Complete this section immediately.
Student No:
Seat Number:
Surname and
initials (optional):
INSTRUCTIONS:
1.
Answer ALL questions.
2.
Calculators may be used but all working must be shown.
3.
Your answers must be written on the question paper in the spaces provided. The lefthand pages may be used for extra space or for rough work and must be indicated as
such.
4.
You must write legibly in black or blue ink. Use of pencil and Tipp-Ex is not allowed.
5.
A periodic table and data sheet are provided.
6.
This question paper consists of 15 pages and 11 questions (i.e. without the cover
page, data sheet and the periodic table). Please check that you have them all.
Question
No.
Internal
Mark
External
Mark
Total Mark
1
2
3
4
5
6
7
8
9
10
11
19
12
7
18
6
11
6
6
4
5
6
100
School of Chemistry
University of KwaZulu-Natal, Howard College Campus
Chem261: Applied Inorganic Chemistry for Chemical Engineers
June 2011 Examination
Page 1
QUESTION 1
(a) Give the definition of the following terms and provide an example of each:
(2)
(i) Tetradentate ligand
(ii) Bridging ligand
(b)
In the periodic table, there is a decrease in the number of the oxidation states from
manganese to zinc. State two reasons why this happens.
(c)
(4)
Give the oxidation state (OS) and coordination number (CN) of the central transition
metal atom in each of the following compounds or complexes:
(i)
[Rh(NH3)4Br]SO4
OS…………………….. CN………………………
(ii)
K2[Pt(acac)4]
OS…………………….. CN………………………
(5)
School of Chemistry
University of KwaZulu-Natal, Howard College Campus
Chem261: Applied Inorganic Chemistry for Chemical Engineers
June 2010 Examination
Page 2
(iii)
[Tc(Br)2(ox)2]
OS…………………….. CN……………………
(iv)
[Os(en)2Br]Br
OS…………………….. CN………………………
(v)
[Cd(CN)4]2OS…………………….. CN……………………
(d)
(e)
Name the following complexes:
(i)
[PdBr6]2−
(ii)
[Pd(Br)2(en)2]
(iii)
Mg[Fe(CO)4Cl4]
(iv)
[Ni(py)2(NH3)2]2+
Write the formula for each of the following complexes:
(i)
Diaquabis(oxalate)cuprate(II)
(ii)
Sodium diamminetetrachlorocobaltate(III)
(4)
(4)
School of Chemistry
University of KwaZulu-Natal, Howard College Campus
Chem261: Applied Inorganic Chemistry for Chemical Engineers
June 2011 Examination
Page 3
(iii)
Dibromotetracarbonyliron(II)
(iv)
diamminetetrathiocyanatomolybdenum(V)
School of Chemistry
University of KwaZulu-Natal, Howard College Campus
Chem261: Applied Inorganic Chemistry for Chemical Engineers
June 2011 Examination
Page 4
QUESTION 2
(a) Write the outer electron configuration of:
(4)
(i) Cu
(ii) Mo
(iii) Sc3+
(iv) Mn2+
(b) From an experimental perspective, write balanced equations for the preparation of:
(4)
(i) Chromium metal by the Thermite reaction.
(ii) Tetraaminecopper(II) sulfate from copper(II) sulphate pentahydrate.
(c)
Hydrochloric acid easily reacts with metals and their oxides. Complete and balance the
following equations. Include the physical state of your products.
(i) HCl(aq) + Cr(s)
(ii) HCl(aq) + Fe2O3(s)
(4)
School of Chemistry
University of KwaZulu-Natal, Howard College Campus
Chem261: Applied Inorganic Chemistry for Chemical Engineers
June 2011 Examination
Page 5
QUESTION 3
(a) (i) Define the term hydration isomers and provide an example.
(1½)
(ii) Name and draw the two types of isomeric structures resulting from geometric
isomerism of the octahedral compound Co(NH3)3Cl3.
(b)
(i) Define a Lewis acid.
(ii) List four key properties of a soft acid as required by Lewis acid-base theory.
(3)
(½)
(2)
School of Chemistry
University of KwaZulu-Natal, Howard College Campus
Chem261: Applied Inorganic Chemistry for Chemical Engineers
June 2011 Examination
Page 6
QUESTION 4
(a) What do you understand by the term “Crystal Field Theory”?
(2)
(b) Use a fully detailed and a well-labelled energy level diagram to show the influence of an
octahedral crystal field on the high-spin Mn2+ ion.
(5)
(c) The splitting of d orbitals on the metal atom in an octahedral field is affected by some
factors. List four main factors that affect ligand field stabilization energy.
(4)
School of Chemistry
University of KwaZulu-Natal, Howard College Campus
Chem261: Applied Inorganic Chemistry for Chemical Engineers
June 2010 Supplementary/Aegrotat Examinations
Page 7
(d) (i) What happens to the energy level diagram when an octahedral crystal of Mn in
QUESTION 4, part (b), has its two trans ligands in an octahedral complex (z ligands)
withdrawn? Explain and also use an energy level diagram to illustrate your answer.
(5)
(ii) What term is used for this phenomenon?
(1)
(iii) What is the reason behind this phenomenon?
(1)
School of Chemistry
University of KwaZulu-Natal, Howard College Campus
Chem261: Applied Inorganic Chemistry for Chemical Engineers
June 2011 Examination
Page 8
QUESTION 5
(a) Explain why [Mo(CO)6]¯ has lower infrared stretching frequencies for the CO ligands
than Tc(CO)6 even though the central metals are isoelectronic.
(b)
(3)
In Tc(CO)6, if three of the CO ligands are substituted with CN ligands, will the
remaining CO ligand’s infrared stretching frequency increase or decrease?
your answer briefly.
Explain
(3)
School of Chemistry
University of KwaZulu-Natal, Howard College Campus
Chem261: Applied Inorganic Chemistry for Chemical Engineers
June 2011 Examination
Page 9
QUESTION 6
(a) (i) With the aid of well-labelled and detailed energy level diagrams, indicate the
occupancy of the orbitals in Fe2+ octahedral high- and low-spin complexes.
(3)
(ii) Hence, calculate the Ligand Field Stabilization Energy (LFSE) for high- and low-spin
complexes in QUESTION 6(a)(i) above.
(3)
School of Chemistry
University of KwaZulu-Natal, Howard College Campus
Chem261: Applied Inorganic Chemistry for Chemical Engineers
June 2011 Examination
Page 10
(b) The magnetic moment of the complex [Fe(CO)6]3+ is 1.72 µB. Use calculations and a
diagram to determine its preferred electron configuration in terms of t2gxegy and suggest
whether CO is a strong (or weak) field ligand from your results.
(5)
School of Chemistry
University of KwaZulu-Natal, Howard College Campus
Chem261: Applied Inorganic Chemistry for Chemical Engineers
June 2011 Examination
Page 11
QUESTION 7
(a) Define the following terminologies in terms of crystal structures:
(i)
Metallic crystals
(1)
(ii)
Ionic crystals
(1)
(b) Figure (X) represents a mineral, rutile,
which primarily contains titanium oxide:
Figure (X)
If the shaded spheres represent the oxide ions and the unshaded ones the titanium
ions, what will be the coordination number for the oxide ion?
(c)
(1)
If the arrangement of the atoms is such that a hexagonal close-packing (hcp) structure
is obeyed and it is a face-centred cubic cell (fcc), what will be the percentage volume
unoccupied by the atoms in a unit cell?
(3)
School of Chemistry
University of KwaZulu-Natal, Howard College Campus
Chem261: Applied Inorganic Chemistry for Chemical Engineers
June 2011 Examination
Page 12
QUESTION 8
(a) Briefly explain the following processes:
(3)
(i) Alpha particle decay (α)
(ii) Negative beta particle decay (β−)
(iii) Positive beta particle decay (β+)
(b) Uranium exits as various isotopes. However, Uranium-238 (238U) is the most common
and stable isotope found in nature.
An example of a less common and less stable
isotope would be Uranium-234 (234U). Give equations to show how the less stable
isotope is obtained from the more stable
238
U isotope.
234
U
(3)
School of Chemistry
University of KwaZulu-Natal, Howard College Campus
Chem261: Applied Inorganic Chemistry for Chemical Engineers
June 2011 Examination
Page 13
QUESTION 9
(a) In a reaction mechanism for a square planar arrangement, the ligand trans to the new
incoming ligand affects the regiospecifity of the reaction and thus the geometry of the
final product. What term is used to express this selectivity?
(b)
(1)
In the reaction below, deduce the major and minor product and state its geometry.
Draw the geometrical structures of the products and clearly indicate the minor and
major products.
Cl
Cl
Pt
Cl
NO2
(3)
1 mole NH3
School of Chemistry
University of KwaZulu-Natal, Howard College Campus
Chem261: Applied Inorganic Chemistry for Chemical Engineers
June 2011 Examination
Page 14
QUESTION 10
South Africa produces uranium from deposits in Precambrian quartz-pebble conglomerates
of the Witwatersrand Basin, at Brakpan and Krugersdorp, Gauteng. Apart from crushing the
ore and concentrating (floatation), how would you leach the ore and eventually convert the
crude product to triuranium octoxide (U3O8) as a final product? Use equations, schemes
and diagrams where necessary.
(5)
School of Chemistry
University of KwaZulu-Natal, Howard College Campus
Chem261: Applied Inorganic Chemistry for Chemical Engineers
June 2011 Examination
Page 15
QUESTION 11
(a) Define the term ‘enthalpy of ionization’.
(1)
(b) Use a Born-Haber cycle to calculate the lattice enthalpy of CaBr2(s) from the information
given below:
Include the drawing of the Born-Haber cycle diagram with relevant
equations in your answer.
(5)
Ca(s) ∆H°sub = 178 kJ mol-1
(sublimation)
Br2(l) ∆H°vap = 31 kJ mol-1
(vapourization)
Br2(g) ∆H°diss = 193 kJ mol-1
(dissociation)
Br(g) ∆H°ea = -331 kJ mol-1
(electron gain)
Ca+(g) ∆H°ie = 590 kJ mol-1
(1st ionization)
Ca+2(g) ∆H°ie = 1145 kJ mol-1
(2nd ionization)
CaBr2(s) ∆H°f = -675 kJ mol-1
(heat of formation)