Transcript Chem. 31 * 9/15 Lecture

Chem. 1B – 11/22 Lecture
Announcements I
• Lab
– No Lab this Wednesday (or Thursday)
• Exam 3
– Next Week on Thursday
– On electrochemistry and Chapter 24
– Help Session Tues. afternoon (joint with PALs??
– I can do 4:00 to 5:00)
Announcements II
• Mastering
– Ch. 24 assignment due 11/26
• Today’s Lecture
– Transition Elements (Ch. 24)
• Properties of Coordination Complexes – light
absorption and magnetic properties - Completing
– Exam 3 Material + Some Practice Problems
– Organic Chemistry (Ch. 20)
Chapter 24 Transition Metals
• Questions – cont. from last time
4. Ti3+ is purple while Ti4+ is uncolored. Explain.
5. For which of the following metals in octahedral
complexes does the ligand NOT play a role in the
number of unpaired electrons?
a) Mn2+ b) Fe3+
c) Co2+
d) Ni2+
6. [Fe(en)3]3+ undergoes a ligand replacement
reaction and forms [FeX6]3-. The new complex
absorbs at shorter wavelengths. What do we know
about the strength of X as a ligand?
Exam 3 Review
• Equations I will give:
DGrxn = DGrxn° + RTlnQ (more Thermo)
DG° = -nFE° and E° = E°cell - (0.0592/n)logQ
• Equations you should know:
q = It (constant I); q = nF
Ecell° = Ered° - Eox°
E (= D) = hc/l
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 DG°, 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)
Exam 3 Review – Chapter 18
• Batteries (Application of Voltaic Cells)
– Be able to relate charge or lifetime to moles
of reactants (q = nF)
– 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 in
first row)
– 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- merisomers exist
– Know what optical isomers are
– Be able to predict the correct number of
isomers
Exam 3 Review – Chapter 24
• Bonding Theory
•
•
•
•
Know where metal ligand bonds come from
Know which d orbitals overlap more with ligand
bonds in octahedral complexes and which overlap
less
Know how overlap leads to a split in the d orbital
energies
Know difference between low spin and high spin
filling of d orbitals
Exam 3 Review – Chapter 24
• Bonding Theory – cont.
•
•
•
•
Know how ligand (e.g. strong vs. weak) affects
filling and D of coordination complexes
Know how metal charge affects D of coordination
complexes
Be able to predict the d orbital electron
configuration of coordination complexes (if known
whether ligand is strong or weak)
Know what causes coordination complexes to
absorb light in visible, plus be able to calculate l
from D or visa versa
Exam 3 Review – Chapter 24
• Bonding Theory – cont.
•
•
Be able to determine number of unpaired electrons
and how that affects magnetic properties of
complexes
Understand why differences in energy levels occur
for other geometries (tetrahedral, square planar)
Exam 3 Review – Questions I
Reaction
Ag+(aq) + e- ↔ Ag(s)
Cu2+(aq) + 2e- ↔ Cu(s)
2H+(aq) + 2e- ↔ H2(g)
Ni2+(aq) + 2e- ↔ Ni(s)
Cd2+(aq) + 2e- ↔ Cd(s)
Fe2+(aq) + 2e- ↔ Fe(s)
E°(V)
+0.80
+0.34
0.00
-0.23
-0.40
-0.45
1. Which of the metals (in oxidation state of zero) in the list
above are oxidized by H+?
a) Ni and Cd
b) Ni only
c) Cd only
d) Cu and Ag
e) Ni, Cd, and Fe
2. In the following cell, the measured voltage is 0.99 V.
Determine x (the concentration of AgNO3(aq) in half of the cell.
cell: Ni(s)|NiCl2(aq, 1.0 M)||AgNO3(aq, x M)|Ag(s)
a) 0.21 M
b) 0.045 M
c) 0.459 M
d) 2.2 M
e) 4.8 M
Exam 3 Review – Questions II
Reaction
Ag+(aq) + e- ↔ Ag(s)
Cu2+(aq) + 2e- ↔ Cu(s)
2H+(aq) + 2e- ↔ H2(g)
Ni2+(aq) + 2e- ↔ Ni(s)
Fe2+(aq) + 2e- ↔ Fe(s)
E°(V)
+0.80
+0.34
0.00
-0.23
-0.45
3. Which of the following reactants can oxidize copper metal
(Cu(s)) under standard conditions?
a) Ag+(aq) b) H+(aq) c) Ni2+(aq) d) Fe2+(aq) e) any of these
4. A voltaic cell is made under standard conditions by Fe(s) and
FeCl2(aq) in one half cell and AgNO3(aq) and Ag(s) in another half
cell. The voltage from the silver (+) to the iron electrode (-) will be:
a) -0.10 V b) +0.10 V c) +0.35 V d) +1.25 V e) +2.05 V
Exam 3 Review – Questions III
5.
The following reaction is an UNBALANCED reaction showing
reactants and products of a redox reaction:
HClO(aq) + Cr(s) ↔ Cl2(g) + Cr3+(aq)
When balanced (can assume acidic conditions), the coefficients in front
of HClO and Cr (with no fractional coefficients anywhere in the
equation) are:
a) 1 and 1 b) 2 and 1 c) 3 and 1 d) 3 and 2
e) 6 and 2, respectively.
6. In coordination complexes, electrons in bonds between ligands and
metals almost always come from:
a) metal s shells
b) metal d shells
c) ligand lone pair electrons
d) ligand inner shell electrons e) ligand sigma bonds
Exam 3 Review – Questions IV
7. Given the complex [Co(NO2)6]4- , give a) oxidation state on Co
b) # d shell electrons, c) # unpaired electrons if you know NO2- is a
strong ligand
8. Can the above compound form any isomers?
Chapter 20 Organic Chemistry
• Introduction
– Organic Chemistry is a major area of study
(we offer 7 organic chemistry classes at the
undergraduate level)
– In ~1 week, we only have time to
introduce basic principles of organic
chemistry
Chapter 20 Organic Chemistry
• Overview
– Nature of Carbon – Carbon Bonds
– Hydrocarbons (structure, naming and
isomers)
– Reactions
– Aromatic Hydrocarbons
– Functional Groups
Chapter 20 Organic Chemistry
• Nature of Carbon – Carbon Bonds
– Carbon is one of the few elements that
form fairly stable bonds with itself
– Most alkanes (hydrocarbons with only
single bonds), while combustible in air
(more stable as CO2 + H2O), have negative
DGfº
– Carbon “likes to” form 4 bonds ([He]2s22p2,
but mostly forms sp to sp3 hybrid bonds)
Chapter 20 Organic Chemistry
• Nature of Carbon – Carbon Bonds
– Simplest hydrocarbon is CH4, methane, in
which sp3 hybridization occurs (tetrahedral
geometry)
– As carbon – carbon bonds are common, in
alkanes, they also occur with sp3
hybridization (tetrahedral for each C atom)