CHEMISTRY 362 Descriptive Inorganic Chemistry. M. Y. Darensbourg. Examination III. April 19, Name:

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1 CHEMISTRY 362 Descriptive Inorganic Chemistry M. Y. Darensbourg Examination III April 19, 2017 Name: An Aggie does not lie, cheat or steal or tolerate (and BTHO) those who do. Signed: Point Group Assignment S = Σm s Spin multiplicity = 2S + 1 μ s.o. = 2 S (S + 1)

2 CHEMISTRY 362 Descriptive Inorganic Chemistry M. Y. Darensbourg Examination III April 19, 2017 Question Points possible Points received I 35 II 15 III 30 IV 35 Total 115 This Exam requires you to combine knowledge from many of the topics covered in this course and to apply the concepts and principles that are in your inorganic chemistry knowledge base. You can do this. Can you believe we are at the third examination?

3 I. 35 pts. This question relates to the similarities between main group, non-metal oxides and transition metal oxides. Fill in the blanks in paragraphs as indicated. You might find some of the answers in these formula and words: SO 3 ; SO 2 ; V 2 O 5 ; VO 2 ; acidic; basic; reducing agent; oxidizing agent; redox reaction; neutralization; C 2, C 3, C 4. A) The oxide of vanadium in its highest oxidation state,, reacts with a sulfoxy species,, and forms the one-electron reduced vanadium oxide,, and a different sulfoxy species,. The balanced chemical equation describing this reaction is give below and the oxidation states of vanadium and of sulfur in each compound are listed below each compound in the equation. + + ox. states: The vanadium oxide that is paramagnetic,, has unpaired electron(s) and the ground state term symbol for vanadium in this oxide is. The vanadium oxide that is diamagnetic,, has unpaired electron(s) and a spin multiplicity of. Its ground state term symbol is. B) Both oxides of sulfur dissolve in water to give acids. Complete the equations describing these reactions, and suggest pka values of each according to Pauling s rule: pk a1 SO 2 + H 2 O SO 3 + H 2 O From these values we conclude that is the stronger acid. Page 1 of 5

4 C) Give the Lewis structures and sketch the VSEPR-predicted geometries of SO 2 and SO 3. SO 2 SO 3 D) The principal rotation axis for SO 2 is and for SO 3 is. The point group assignment for SO 2 is and for SO 3 is. E) Give at least two resonance structures for SO 2 and use formal charge criteria to select the best structure. F) The hybrid orbitals on S that are used for the S-O sigma bond overlap in SO 3 are. G) Sketch the orbital overlap that defines one π-bond in SO 3. II. 15 pts a) Reported in 2015 in the journal of Physical Chemistry was an experimental and computational study of the interaction of ammonia and SO 3. A graphic in that paper is shown to the right. Label the type of bond or interaction between S and O at 1.450Å; between N and S at 1.975Å; and between N and H at 1.862Å. Terms you might consider using are: H-bonding, dipole-dipole interaction; Lewis acid/base interaction; ionic bonding; covalent bond, etc. b) Neglecting the second NH 3 molecule, what is the principal rotation axis and the symmetry point group of the SO 3 -NH 3 adduct? Page 2 of 5

5 III. 30 pts. A) Due to their ability to exist in various oxidation states, transition metals typically form multiple types of oxides. Give the oxidation states of Fe and Cu and the d-electron count with each in the following oxides. Oxides Oxidation State(s) of M d-electron count of Fe or Cu FeO Fe 2 O 3 Fe 3 O 4 [FeO 4 ] 2- Cu 2 O CuO Cu 2 O 3 B) These oxides result from complete 4-electron reduction of O 2, yielding O 2 anions. However, partial or incomplete one-electron reduction of O 2 yields O 2, a molecular anion. Give the MO assignment (KKσ 2 2s σ* 2s...) of O 2 and O 2, and for each give the bond order and spin-only magnetic moment. B.O. µ so O 2 O 2 C) Copper forms a compound of formula CuO 2, similarly to ZnO 2, while ZnO 2 is colorless and diamagnetic, CuO 2 is a dark olive green and has μ s.o. = 1.73 BB. As Zn can only have oxidation state of zero, Zn 0 (as in the metal) or 2+ (as in Zn 2+ ), predict the electronic structure (Lewis structure) of the oxygen species in ZnO 2 and CuO 2, and give the oxidation state of Cu in this compound. D) The unit cell of one of the copper oxides is given here. What is the formula of this copper oxide? How did you arrive at your answer? Page 3 of 5

6 IV. 35 pts A) For the electrochemical cell at right, a) Identify the cathode and anode, and give the half reactions that occur at the cathode and anode, respectively. b) Indicate the direction of electron flow in the external circuit. c) Calculate the cell potential under standard conditions. d) Calculate the free energy of the reaction achievable. e) Calculate the K eq for such a set-up. f) The salt bridge is comprised of NaNO 3. Indicate the direction of ion movement; i.e., towards which compartment do the Na + ions migrate? B) Calculate the cell potential for the disproportionation of Cu + to Cu 0 and Cu 2+ under standard aqueous conditions. Page 4 of 5

7 C) The electrolysis of sodium chloride as a melt produces Na 0 metal and chlorine gas, Cl 2. In contrast, the electrolysis of NaCl dissolved in water produces 2 gases. Give balanced chemical equations for both processes. D) Table 5.1 of your text gives values for the ionization energies for Li 0, Na 0, and Cs 0, as well as the standard Reduction Potentials; these are repeated below. Give equations that define these thermodynamic processes; don t forget to state the conditions used for the experimental measurements. In a couple of sentences rationalize the trend observed for the IPE and contrast to the trend or discontinuity in the Standard Reduction Potential. Li Na Cs Ionization Potential Energy kj/mol Standard Reduction Potential Volt Page 5 of 5