BARCODE:
SCHOOL OF CHEMISTRY & PHYSICS
UNIVERSITY OF KWAZULU-NATAL, WESTVILLE CAMPUS
CHEM210: INORGANIC CHEMISTRY
JUNE 2014 MAIN EXAMINATION
STUDENT NO.
SEAT NUMBER:
DURATION: 1½ HOURS
TOTAL MARKS: 50
External Examiner or Moderating Board:
Internal Examiner:
Prof. H.B. Friedrich (UKZN)
Dr. V.O. Nyamori (Module Coordinator)
Dr. S. Singh
SECTION A
QUESTION NO.
1
2
3
4
Total
17
9
11
13
50
INTERNAL MARK
EXTERNAL MARK
TOTAL MARKS
INSTRUCTIONS
1.
Non programmable calculators may be used but all working must be shown.
2.
You must write legibly in black or blue ink. Pencils and Tipp-Ex are not allowed.
3.
This question paper consists of 9 pages (including the cover page) and 4 questions. Please
check that you have them all.
4.
You will also require a copy of Section B.
5.
A periodic table and a data sheet are provided separately.
1
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2014 Main Examination Session, CHEM210 Inorganic Chemistry
Section A
Question 1 (17 marks)
(a)
(b)
Name the complexes:
(i)
[CoCl(NH3)5]Cl2
(1)
(ii)
Na2[PtCl2(NH3)2]
(1)
Write the formula of the following compounds:
(i)
diamminetetra(isothiocyanato)chromate(III)
(1)
(ii)
tris(ethylenediamine)rhodium(III)
(1)
2
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2014 Main Examination Session, CHEM210 Inorganic Chemistry
Section A
(c)
Consider the complex trans-[Fe(CN)4Cl2]3- and answer the following questions:
(i)
Sketch the structure of the complex.
(2)
(ii)
Give the formula and the complete name of the sodium salt of the complex.
(1)
(iii)
What is the oxidation state of Fe in this complex?
(1)
(iv)
How many d electrons are associated with the Fe in this complex?
(1)
3
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2014 Main Examination Session, CHEM210 Inorganic Chemistry
Section A
(d)
Show with the aid of fully named structures, the type of isomerism exhibited by:
(i)
[CoCl3(NH3)3].
(4)
(ii)
[Co(NO2)(NH3)5]2+
(4)
4
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2014 Main Examination Session, CHEM210 Inorganic Chemistry
Section A
Question 2 (9 marks)
(a)
Calculate the energy (in kJ per mole of photons) of a spectroscopic transition, the
corresponding wavelength of which is 550 nm.
(b)
(i)
On a single graph, plot the radial distribution function, 4πr2R(r)2, versus distance r
from the nucleus, for the 1s, 2s, and 3s atomic orbitals of the hydrogen atom.
(ii)
(b)
(2)
State the number of radial nodes present for each of the 1s, 2s, and 3s orbitals.
Describe the bonding in PF5 using valence bond theory.
5
(3)
(1½)
(2½)
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2014 Main Examination Session, CHEM210 Inorganic Chemistry
Section A
Question 3 (11 marks)
(a)
(b)
Consider the Li2 molecule:
(i)
Write its molecular orbital configuration.
(1½)
(ii)
Determine whether the ion exists. (Hint: Calculate bond order).
(1½)
(i)
Write the molecular orbital (MO) energy diagram for the CN- molecule.
6
(4)
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2014 Main Examination Session, CHEM210 Inorganic Chemistry
Section A
(ii)
Determine the bond order for this ion.
(1)
(iii)
Compare your result in (ii) with the predicted bond order from a Lewis structure.
(2)
(iv)
Name a heteroatom diatomic chemical species that is isoelectronic with CN-.
(1)
7
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2014 Main Examination Session, CHEM210 Inorganic Chemistry
Section A
Question 4 (13 marks)
(a)
Consider the complex, [Mn(NCS)6]4-:
(i)
With the aid of fully labelled energy level diagrams, indicate the occupancy of the
orbitals in the high-spin and low-spin state of the complex.
(ii)
(3½)
If the magnetic moment of the complex is 6.06 μB, determine its preferred electron
configuration.
(3½)
8
University of KwaZulu-Natal, School of Chemistry and Physics, Westville Campus
June 2014 Main Examination Session, CHEM210 Inorganic Chemistry
Section A
(iii)
Estimate the ligand field stabilization energies (LFSE) for both the high-spin and low
spin states of the complex.
(b)
(3)
Using the spectrochemical series, write down the preferred electronic configuration, in the
form, t2geg for the complexes, [Fe(OH2)6]2+ and [Fe(CN)6]3-.
9
(3)
BARCODE:
SCHOOL OF CHEMISTRY & PHYSICS
UNIVERSITY OF KWAZULU-NATAL, WESTVILLE CAMPUS
CHEM210: INORGANIC CHEMISTRY
JUNE 2014 MAIN EXAMINATION
STUDENT
NO.
SEAT NUMBER:
DURATION: 1½ HOURS
External
Board:
Examiner
TOTAL MARKS: 50
or
Moderating Internal Examiners:
Dr. V.O. Nyamori (Module Coordinator)
Prof. H.B. Friedrich and Dr S.O. Ojwach
Dr. S. Singh
SECTION B:
Total for Section B: 50 Marks
QUESTION NO.
1
2
3
4
Total
14½
6
15
14½
50
INTERNAL MARK
EXTERNAL MARK
TOTAL MARKS
INSTRUCTIONS
1.
Non programmable calculators may be used but all working must be shown.
2.
You must write legibly in black or blue ink. Pencils and Tipp-Ex are not allowed.
3.
This question paper consists of 6 pages (excluding the cover page) and 4
questions. Please check that you have them all.
4.
You will also require a copy of Section A.
5.
A periodic table and a data sheet are provided separately.
6.
Answer on the question paper.
QUESTION 1
(a)
Give the definition of the following terms and in each case provide an example
which fully illustrates the terminology. (Hint use diagrams or formula where
appropriate.)
(b)
(i) Hypervalency
(1½)
(ii) Metallic radius of sodium
(1½)
(iii) Amorphous solid
(1½)
From your laboratory experience, give the reagents and products, and write balanced
equations for the preparation of:
(c)
(i) [Co(NO2)6]3ˉ
(3)
(ii) chromium metal by the Thermite reaction
(3)
Sodium chloride and other solid ionic salts form cubic unit cells. State two main
factors that will affect their formation of gaseous ions from the solids.
(d)
(2)
What are the two major forces that the above ionic structure experience? (2)
1
QUESTION 2
(a)
Define the following term:
(i)
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
the relevant equations in your answer.
(5)
Ca(s) ΔH°sub = 178 kJ mol-1
(sublimation)
Br2(l) ΔH°vap = 31 kJ mol-1
(vapourization)
Br2(g) ΔH°diss = 193 kJ mol-1
(dissociation)
Br(g) ΔH°ea = -331 kJ mol-1
(electron gain)
Ca+(g) ΔH°ie = 590 kJ mol-1
(1st ionization)
Ca+2(g) ΔH°ie = 1145 kJ mol-1
(2nd ionization)
CaBr2(s) ΔH°f = -675 kJ mol-1
(heat of formation)
2
QUESTION 3
The figures below represent the calcium fluoride salt from the fluorite mineral (Figure 1)
and a mineral, rutile, which primarily contains titanium oxide (Figure 2):
Figure 1
Figure 2
(a) In Figure 1 the smaller spheres represent the calcium ions and the larger ones the
fluoride ions, while in Figure 2, the lighter spheres represent the titanium ions while
the shaded ones represent the oxide ions.
(i) What is the coordination number (CN) of the calcium, fluoride, titanium and
oxide ions in Figures 1 and 2?
(2)
Calcium ions CN: ………… Fluoride ions CN: ….……..
Titanium ions CN: ….…….. Oxide ions CN: ….…………
(ii) In terms of packing of atoms (or group of atoms) and the assumption that there
is minimal repulsion on the anions, what is the implication when the anion
coordination number increases?
(2)
3
(ii) If titanium oxide is a close-packed solid structure composed of spheres with
radius r, calculate the maximum radius (rh) of a sphere that may be
accommodated in an octahedral hole. Draw a relevant geometric structure to
show your answer.
(b)
(3)
A metal with a cubic close-packed (ccp) structure has a face-centred unit cell (FCC)
and a density of 19.3 g cm-3. The cubic length dimension is 408 pm (4.08 Å).
(i) Sketch its unit cell and calculate the number of lattice points.
calculations.
Show all your
(2)
(ii) Calculate the molar mass and suggest the metal being investigated. Show all
your calculations.
(6)
4
QUESTION 4
(a) Provide balanced equations to show how nitrogen gas can be prepared. Fill in the
blanks and balance the equations.
(4½)
(i) In the laboratory using ammonium chloride an one of the reagent
………………..+ …………….
N2 (g) + …………… + ……………
(ii) By the thermal decomposition of ammonium dichromate.
……………………..(Heat)
N2 (g) + ……………… + …………
(b) Phosphorous is able to form pentahalides. Why does nitrogen not form pentahalides?
(2)
(c) What are the three common allotropes of phosphorus? Name and draw their general
structure.
(3)
5
(d) Make general and brief comments on the following properties of the elements as you
move down Group 14.
(i) Electronegativity
(2)
(iii) Metallic character
(2)
6