Students are requested, in their own interests, to write legibly.

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1 School of Chemistry UNIVERSITY OF KWAZULU-NATAL, WESTVILLE CAMPUS CHEM210: INORGANIC CHEMISTRY DURATION: 3 HOURS TOTAL MARKS: 100 Internal Examiner: Dr W E van Zyl Moderating Board: Dr V O Nyamori Dr I N Booysen INSTRUCTIONS: This paper consists of 15 pages and 5 questions. A Periodic Table and Data Sheet are also supplied at the end of this paper. Calculators may be used, but all work must be shown. Use the overleaf pages should you run out of space, CLEARLY indicate if it needs to be marked as well as the number of the question. ANSWER ALL QUESTIONS DIRECTLY ON THE PAPER. Students are requested, in their own interests, to write legibly. STUDENT NUMBER: SEAT NO: Questions TOTAL Internal Marks External Marks

2 QUESTION 1 a. On a single graph, plot the radial distribution function, 4πr 2 R(r) 2, versus distance r from the nucleus, for the two atomic orbitals that are defined by the following quantum numbers: n=2, l=0 and n=3, l=2. Label the plots. (4) b. Name the FOUR fundamental forces in Nature. (2) c. Fill an Aufbau diagram with the four valence electrons of carbon, and give a set of quantum numbers (n, l, m l, m s ) that uniquely defines each electron within the respective orbitals. (2) 2

3 QUESTION 1 (Cont.) d. Write the electron configuration of the following chemical species. Use the abbreviated noble gas format and list only the valence electrons. I P 3- Si 4+ Br Co 3+ (5) e. Draw each of the two orbitals dx 2 -y 2 and dxy on a separate axes system. (2) 3

4 QUESTION 1 (Cont.) f. Draw the Lewis-dot structure of the HPSe 4 2- anion and assign a formal charge to the P and all the Se atoms. (3) g. Use VSEPR theory to determine the name of the molecular geometry/shape of each the following ions and molecule. State whether the chemical species is polar or non-polar. i) nitrate ion, ii) triiodide ion, iii) krypton tetrachloride. (3) [21] 4

5 QUESTION 2 a. Illustrate bonding in the H 2 S molecule in terms of Valence Bond Theory. Your answer should indicate the filled atomic orbitals of S atom in the ground-state, followed by 'promotion' showing the type of hybridization that occurs among the appropriate orbitals. (3) b. Give the systematic IUPAC names for the following three coordination complexes: (3) (i) (NH 4 ) 4 [CoCl 2 Br 2 (CN) 2 ] (ii) K 2 [Cu(dppm)(H 2 O) 2 ] (iii) [Au(NH 3 ) 2 ][Ag(CN) 2 ] c. Give the formula for the following three coordination complexes: (i) lithium dicarbonylbis(oxalato)vanadate(ii) (3) (ii) hexaamminechromium(ii) carbonate 5

6 QUESTION 2 (Cont.) (iii) tris(acetylacetonate)iron(iii) d. Write the ionization isomer, as a formula, of [Pt(NH 3 ) 3 (OH)]Br. (1) e. Draw the i) cis isomer of the complex [CrBr 2 (H 2 O) 4 ], and the ii) mer isomer of the complex [CrBr 3 (H 2 O) 3 ] (3) [13] 6

7 QUESTION 3 a. Construct a molecular orbital (MO) energy diagram for the Cl + 2 ion and determine the bond order. (4) 7

8 QUESTION 3 (Cont.) b. Construct the molecular orbital (MO) energy diagram for the CO molecule, and show the HOMO and LUMO orbitals. From this diagram determine the bond order. Compare the C-O bond in both CO and CO 2 and comment which of these two species will have the longest bond length and strongest relative bond strength. (6) c. List any four chemical species that are isoelectronic with selenide ion, Se 2- (2) 8

9 QUESTION 3 (Cont.) d. Use the same barycentre to draw two crystal field splitting diagrams showing how five degenerate d-orbitals of a transition-metal undergo a change in energy when placed in an octahedral and a tetrahedral crystal field environment. Show both oct and tetr on the drawing. (4) e. In crystal field theory, an octahedral complex within a d 6 system can have either configuration t 6 2g e 0 g (low-spin) or t 4 2g e 2 g (high-spin). Calculate the Crystal Field Stabilization Energy (CFSE) for each system. (3) [19] 9

10 QUESTION 4 a. Draw and label the four unit cells each representing a different Bravais lattice within the orthorhombic crystal system. (4) b. Aluminum (Al) has a ccp arrangement of atoms as shown below. The radius of Al is 1.432Å (143.2 pm). Calculate the lattice parameter, a, of the unit cell and the density of solid Al (atomic weight = 26.98). Show all work. (4) 10

11 QUESTION 4 (Cont.) c. NiO crystallises in the rock salt structure. Draw the structure and then tabulate how many cations and anions there are, respectively, in the body, face, edge and vertex (corners) of the unit cell and then sum them to determine the total number of NiO formula units (Z) in the unit cell. (4) d. Use the Born-Mayer equation to estimate the lattice enthalpy of NaCl. Data are provided, also consult attached Data Sheet: d (or ρ) = 34.5 pm; d o (or r o ) = 282 pm; Madelung constant = (4) 11

12 QUESTION 4 (Cont.) e. Use the data below to calculate the formation enthalpy, H f, for LiF(s) by making use of a Born-Haber cycle. Show all reactions in the cycle. H / (kj/mol) Sublimation of Li(s) +161 Ionisation of Li(g) +531 Dissociation of F 2 (g) +158 Electron gain by F(g) -328 Lattice enthalpy of LiF(s) (5) [21] 12

13 QUESTION 5 P 4 O 6 a. Make brief, accurate, and unique descriptive comment for EACH of the following phosphorus oxides and -acids. (1 mark) P 4 O 10 H 3 PO 2 (1 mark) H 3 PO 3 H 3 PO 4 (8) 13

14 QUESTION 5 (Cont.) b. Make two brief comments on each of the following key phrases and trends regarding the Group 14 elements (C, Si, Ge, Sn, Pb). i) catenation; ii) coordination numbers; iii) metallic character; iv) multiple bonds (2x4=8) 14

15 QUESTION 5 (Cont.) c. Make a brief, accurate, and unique descriptive comments for EACH of the following Group 16 elements: Oxygen Sulfur Selenium Tellurium Polonium (10) [26] 15