Chem. 1B – 11/19 Lecture

Announcements I Mastering Chemistry –Chapter 24 Assignment due Nov. 29th Lab –Experiment 10 due; Starting Experiment 14 (last one) –Quiz on Experiment 12/14 + Chapter 24 material (mostly multiple choice) Exam 3: –Example Exam from other instructors posted (will link to key when available) –Format similar to exams 1 and 2 (multiple choice with one 12 point problem)

Announcements II Exam 3 – cont. –Will cover up Chapter 18 (~65%) and 24 (through section 24.4 isomers - ~35%) – review later –Help Sessions: Only PAL this time –Section 7 exam in lab room –Review homework, quizzes, in class problems Today’s Lecture –Review of Exam Topics –Coordination Compounds Isomers (last set of example problems) Crystal Field Theory

Chapter 24 Transition Metals Coordination Complex – Isomers –Compare MABCD and MX 2 YZ isomers –Questions 1.In what way is [Cr(NH 3 ) 5 Br]Cl 2 different from [Cr(NH 3 ) 5 Cl]BrCl? 2.How many different isomers are present for the square planar compound [Pt(NH 3 ) 2 ClBr]?

Exam 3 Review Equations I will give:  G rxn =  G rxn ° + RTlnQ (more Thermo)  G° = -nFE° and E° = E° cell - (0.0592/n)logQ Equations you should know: q = It (constant I); q = nF  G rxn ° = -RTlnK

Exam 3 Review – Chapter 18 Redox Reactions –Be able to determine oxidation states –Determine which element is being reduced and which is being oxidized –Know all steps in reaction balancing and be able to apply (see example questions) –Know three ways in which redox reactions can occur (beakers, voltaic cells, electrolytic cells

Exam 3 Review – Chapter 18 Voltaic Cells –Know components of voltaic cell (anode, cathode, cell bridge, rest of circuit) –Know charge of and reaction type at each electrode –Know flow (direction) of electrons and ions –Know purpose of voltaic cell –Know cell notation

Exam 3 Review – Chapter 18 Standard Electrode (Reduction) Potentials –Know basis (how it could be measured) –Know standard conditions –Be able to use table to: Determine E° cell (from combining two standard electrodes) + reaction direction Know what makes a good reducing/oxidizing agent What metals can be oxidized in acid

Exam 3 Review – Chapter 18 Relating Thermodynamics to Cell Potential –Be able to convert between  G°, K, and E° –Know standard conditions –Use of the Nernst Equation: For calculation of E cell (non-standard conditions) For determination of concentration For determination of E° cell (from E measured and Q)

Exam 3 Review – Chapter 18 Batteries (Application of Voltaic Cells) –Be able to relate charge or lifetime to moles of reactants –Know requirements for rechargeable batteries –Know fuel cell basics Electrolysis –Know main differences with voltaic cells –Be able to predict reduction/oxidation reactions

Exam 3 Review – Chapter 18 Corrosion –Understand tendency of metals to oxidize –Understand requirement of sacraficial metals

Exam 3 Review – Chapter 24 Transition Metal Names –Know names of row 4 elements + d8 to d10 (row 5 and 6) Transition Metal Properties –Know electron configurations of transition metals plus ions (including rule exceptions) –Know size (mostly decreases across row) and oxidation state trends

Exam 3 Review – Chapter 24 Coordination Complexes –Know requirement for ligands –Know types of ligands (mono-, bi-, polydentate) –Know major geometries (linear, square planar, tetrahedral, octahedral) plus associated ligand numbers and structures –Know how to relate name to formulas (we are not worrying about bis-, linkage ligands in names, and a table of latin roots will be provided)

Exam 3 Review – Chapter 24 Coordination Complexes - Isomers –Know what structural isomers are –Know requirement for linkage isomers –Be able to tell if cis- trans- or fac- mer- isomers exist –Know what optical isomers are –Be able to predict the correct number of isomers

Chapter 24 Transition Metals Coordination Complex – Bonding Theory (Not on Exam 3) –Valence Bond Theory and Crystal Field Theory –For covalent bonds (valence bond theory) overlap occurs between atomic orbitals from each atom (e.g. 1s in H and sp 3 hybrid orbitals in C in CH 4 ) –For coordination compounds, however, electrons come fully from ligands

Chapter 24 Transition Metals Coordination Complex – Bonding Theory – cont. –For example, in [Zn(OH) 4 ] 2-, bonding orbitals can come from empty 4sp 3 on Zn 2+ and filled 2p orbitals on O. (All electrons from O) –However, for square planar and octahedral complexes, non empty d orbitals play a role (hybrid orbitals must have d character)

Chapter 24 Transition Metals Coordination Complex – Bonding Theory – cont. –To understand how electrons in the d shells influence bonding, we must understand the shapes of d orbitals –Two different classes of d orbitals occurs Off axes orbitals x y z x y z d xy – lies in xy plane x y z d xz d yz

Chapter 24 Transition Metals Coordination Complex – Bonding Theory – cont. –Two different classes of d orbitals occurs On axes orbitals x y z x y z d x^2 – y^2 d z^2

Chapter 24 Transition Metals Coordination Complex – Bonding Theory – cont. –In octahedral binding, because the ligands bring the electrons, lower energy results when the binding axes orbitals (d z2 and d x2-y2 ) are UNFILLED –Or alternatively, the ligands cause a split in energy levels of d shell orbitals E Free atom Metal in octahedral complex On axis Off axis 

Chapter 24 Transition Metals Coordination Complex – Bonding Theory – cont. –How does d orbital splitting affect coordination complexes? –Electrons go to low energy states first –Example: [Cr(CN) 6 ] 3- has 4 – 1 = 3 d shell electrons – they should occupy the three off- axes orbitals On axis Off axis

Chapter 24 Transition Metals Coordination Complex – Bonding Theory – cont. –When we add more than 3 electrons (e.g. 4 electrons), there are two possibilities: fill bottom orbitals first or go to top orbitals –Filling depends on  gap (larger leads to “low spin” states – first shown, while smaller leads to “high spin” states – second shown)