chem. 1b – 11/19 lecture. announcements i mastering chemistry –chapter 24 assignment due nov....

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 MX2YZ isomers

– Questions1. In what way is [Cr(NH3)5Br]Cl2 different

from [Cr(NH3)5Cl]BrCl?

2. How many different isomers are present for the square planar compound [Pt(NH3)2ClBr]?

Exam 3 Review

• Equations I will give:Grxn = Grxn° + RTlnQ (more Thermo)

G° = -nFE° and E° = E°cell - (0.0592/n)logQ

• Equations you should know:q = It (constant I); q = nFGrxn° = -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


• 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


• 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


• 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 Ecell (non-standard conditions)

• For determination of concentration

• For determination of E°cell (from Emeasured and Q)


• 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


• Corrosion– Understand tendency of metals to

oxidize– Understand requirement of sacraficial

metals


• 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


• 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)


• 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


• 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 sp3 hybrid orbitals in C in CH4)

– For coordination compounds, however, electrons come fully from ligands


• Coordination Complex – Bonding Theory – cont.

– For example, in [Zn(OH)4]2-, bonding orbitals can come from empty 4sp3 on Zn2+ 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)



– 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

yz

x

yz

dxy – lies in xy plane x

yz

dxz dyz



– Two different classes of d orbitals occurs

• On axes orbitals

x

yz

x

yz

dx^2 – y^2 dz^2



– In octahedral binding, because the ligands bring the electrons, lower energy results when the binding axes orbitals (dz2 and dx2-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 axisOff axis



– 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 axisOff axis



– 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)

chem. 1b – 11/19 lecture. announcements i mastering chemistry –chapter 24 assignment due nov....

Documents

review chapter

cell potentialbe able

review laterhelp sessions

example exam

cell bridge

redox reactionsbe able

calculation of ecell

d10 row