1. Draw the molecular geometry and indicate any deviations from ideal VSEPR coordination angles. Give the point group for each molecule.

Size: px

Start display at page:

Download "1. Draw the molecular geometry and indicate any deviations from ideal VSEPR coordination angles. Give the point group for each molecule."

Dennis Hubbard
5 years ago
Views:

1 1 Inorganic Chemistry 411/ minutes; 200 points total Show your work for partial credit. Final Exam 1. Draw the molecular geometry and indicate any deviations from ideal VSEPR coordination angles. Give the point group for each molecule. (a) [10 pts] CH 2 Cl 2 [10 pts] XeO 3 Td coordination, C 2v trig pyramidal, C 3v OXeO < [7 pts] Is either of the above molecules chiral? Explain using symmetry rules. No, they both have mirror plane operations. 2. (a) [12 pts] Write down a Born-Haber analysis (give all the reaction steps) needed to estimate H f for CaO(s) from the elements in standard states. Label each reaction step with an appropriate energy term (such as I, E a, ΔH L, etc). Ca(s) Ca (g) ΔH at (Ca) Ca(g) Ca 2+ (g) + 2 e - I 1 (Ca) + I 2 (Ca) ½ O 2 (g) O(g) ½ D 0 (O-O) O(g) + 2 e - O 2- (g) - (E a1 (O) + E a2 (O)) Ca 2+ (g) + O 2- (g) CaO (s) - ΔH L (CaO) Ca(s) + ½ O 2 (g) CaO (s) ΔH f (CaO(s)) Correct reactions steps [5] Correct label for energetics (I, Ea, ΔHL, etc) [4] Correct summation and signs [3] [7 pts] Is CaO(s) more or less soluble in polar solvents than KF (s)? Explain briefly.

2 2 Much less soluble. CaO has a much larger lattice enthalpy due to the higher ion charges, this opposes ion solvation. 3. (a) [14 pts] Construct an MO diagram for the cyanide anion, CN (g), including valence atomic and molecular orbitals, symmetry labels, and the electron filling of the MO's. CN is isoelectronic and isolobal with CO. See the MO for CO in text Fig [7 pts] Draw a figure showing the geometry of the LUMO orbital on CN. [5 pts] Show with a simple picture how the LUMO in part can act as a π acceptor for transition metal cations.

3 3 4. A Latimer diagram for Cl at ph=0 is: 1.20 V ClO 4 ClO 3 HClO 2 HClO Cl 2 Cl (a) [10 pts] What is the standard potential for reduction of ClO 3 to Cl at ph=0? [2(1.18) + 2(1.67) + 1(1.63) + 1(1.36)] / 6 = V [10 pts] Does Cl 2 disproportionate spontaneously in aqueous acid? Explain. No. The reaction Cl 2 Cl - + HClO has a negative potential (1.36 V 1.63 V). Reactions to form chloride and HClO 2 or Cl(V) or Cl(VII) also have a negative potential. [10 pts] Write a balanced half-reaction for the reduction of HClO to Cl 2 in acidic solution. 2 e - + 2H HClO Cl H 2 O (d) [10 pts] Calculate the potential for the half-reaction in part at ph = 3. The Nernst equation is E = E 0 (0.059 V/ n) log Q E = (3)(0.059) = V 5. (a) [6 pts] Write out the full name of the octahedral complex [Mn(NH 3 ) 6 ] 2+ hexamminemanganese(ii) or hexaamminemanganese(2+) [10 pts] Write a d orbital energy level diagram for BOTH the strong-field (low spin) and weak-field (high spin) cases for the complex in part (a). Label the d- orbitals with (z 2, x 2 -y 2, xy, xz, and yz) and also give the orbitals symmetry labels.

4 4 [10 pts] Calculate the ligand field stabilization energies (LFSE) in terms of O for BOTH of the two electron configurations in part (a). High spin LFSE = zero; low spin is LFSE = 2.0 Δ O (d) [8 pts] How would you experimentally determine the actual configuration (high or low-spin) for an O h complex of Mn(II)? Magnetic moment should be proportional to sqrt [N(N+2)]. [8 pts] Trying to measure LFSE by calorimetry is not a good method. [4 pts if this] 6. (a) [10 pts] Write a balanced reaction showing how H 2 is generated on an industrial scale. CH 4 (g) + H 2 O (g) CO (g) + 3 H 2 (g) Or C (s) + 2 H 2 O (g) CO 2 (g) + 2 H 2 (g) Or, electrolysis is OK [8 pts] Describe briefly 2 important ways that hydrogen bonding affects our daily lives. 1. Lower density of ice than water

5 5 2. DNA replication 3. High bp of liquid water. 7. [4 pts each] Circle the ONE best choice. (a) Wurtzite structure has the stacking sequence of (AaBb) n, where uppercase letters are anions and lowercase are cations. What is the coordination geometry around anions in the lattice? (1) tetrahedral (2) square planar (3) octahedral (4) trigonal prismatic (5) linear (6) trigonal bipyramidal The following complexes are all high spin. Which has a LFSE equal to zero? (1) [Fe(OH 2 ) 6 ] 2+ (2) [Fe(OH 2 ) 6 ] 3+ (3) [Mn(OH 2 ) 6 ] 2+ (4) [Co(OH 2 ) 6 ] 3+ (5) all these complexes have the same LFSE (either choice was OK) Which of the following octahedral complexes has two geometric isomers? (1) [FeCl(OH 2 ) 5 ] 2+ (2) [IrCl 3 F 3 ] 2- (3) [RuCl 4 (bipy)] 2- (4) [CoBr 2 Cl 2 (NH 3 ) 2 ] + (5) [W(CO) 6 ] (6) [CrCl 5 (NH 3 )] 2- (d) Which ligand will form the strongest complex with the hard acid Al 3+? (1) O 2- (2) S 2- (3) Se 2- (4) Te 2- (5) all complexes will have the same K f (e) (f) (g) Which ligand is a π-acceptor with a strong ligand field effect? (1) N(CH 3 ) 3 (2) H (3) CN (4) Cl (5) NH 3 (6) P(CH 3 ) 3 Based on d electron configurations, which of the following is NOT likely to be square planar? (1) [AgCl 4 ] (2) [AuF 4 ] (3) [Pd(CN) 4 ] 2- (4) [RhF 4 ] 2- (5) [PtCl 4 ] 2- The anion XeF 5 shows only a single 19 F NMR peak over a wide temperature range (ignoring coupling to 129 Xe). Which geometry is consistent with this data? (1) trigonal bipyramidal (2) square pyramidal (3) pentagonal planar (4) linear (5) rhomboidal (6) cubic (h) Which of the following will rapidly react with water to form H 2? (1) O 2 (2) F 2 (3) HF 2 (4) CH 4 (5) SF 6 (6) CaH 2 (i) Using Pauling s rules, what is the expected pk a for nitrous acid, HNO 2?

6 6 (1) 0 (2) 1 (3) 3 (4) 5 (5) 7 (6) 8 O h E 8C 3 6C 2 6C 4 3C 2 i 6S 4 8S 6 3 h 6 d A 1g x 2 +y 2 +z 2

7 7 A 2g E g (z 2, x 2 -y 2 ) T 1g T 2g (xz, yz, xy) A 1u A 2u E u T 1u (x, y, z) T 2u

Inorganic Chemistry 411/511 Final Exam Name 115 minutes; 200 points total Show your work for partial credit.

Inorganic Chemistry 411/511 Final Exam Name 115 minutes; 200 points total Show your work for partial credit. 1 1. Draw the molecular geometry and indicate any deviations from ideal VSEPR coordination angles.