Chem 30A Fall 2001 Prof Garrell Week 0 1 Synopsis Goals and Assignments for Sept 26 through Oct 5 2001 REDOX and ELECTROCHEMISTRY TOPICS Oxidation reduction and oxidation numbers oxid states intro to formal charge Balancing redox reactions by the half reaction method G and electrochemical work Galvanic electrolytic cells The cell potential under standard conditions E Faraday s law Relationship between free energy and cell potential The Nernst equation Applications of the Nernst equation determining Q and concentrations Yields from electrolytic processes Be able to assign oxidation numbers states for atoms in inorganic and organic molecules and ions and to use them to identify species that are oxidized and reduced Be able to recognize the correlation between the number of C H and C O bonds and the oxidation state of carbon Be able to write oxidation and reduction half reactions and combine them to obtain a balanced chemical reactions b the net cell reaction and c the standard potential E Understand cell diagrams and be able to identify the oxidation and reduction half reactions and determine whether the cell is galvanic or electrolytic Be able to use Faraday s law to quantify the products of electrolysis or determine the current or time necessary to produce a specified amount of product Be able to calculate the free energy change and equilibrium constant from the cell potential G nFE G nFE G RTlnK ln Q Understand the Nernst equation E E o RT nF Be able to apply the Nernst equation to determine cell potentials under nonstandard conditions e g concentration cells Be able to use the Nernst equation to determine Q and concentrations including pH Understand how the cell potential is related to the spontaneity of a process and the proximity of a reaction to equilibrium Be able to determine the product yield from an electrolytic process GOALS Redox Electrochem synopsis p 2 of 3 Redox Electrochem synopsis p 3 of 3 ASSIGNMENTS READINGS Munowitz Sections 3 3 17 1 17 3 through 17 9 Brown Foote Sections 6 5A not 6 5B or C OTHER RESOURCES Weeks s Pushing Electrons Section on formal charge pp 20 25 Vining CD Supporting Concepts Formal Charge Optional Harcourt web tutorial Formal Charge PROBLEMS You should be able to balance reactions like those in the assigned problems If necessary do additional practice problems 3 5 7 12 Munowitz Ch 17 1 2 4 6 8 11 13 15 18 19 25 26 29adh 34 36 38 40 Brown Foote 1 31 Additional Problems A and B A Write Lewis structures for each of the following compounds If needed review the section in Munowitz on Lewis structures or review the material in the Pushing Electrons workbook Note that we ll be recapping Lewis structures in Week 2 a CH3CH2OH ethanol b CF3COOH trifluoroacetic acid or TFA c CH3 2CO acetone d CH2Cl2 dichloromethane e C6H6 benzene In which compound is the boldface type of carbon atom in the highest oxidation state In the lowest oxidation state optional Looking ahead can you name the functional group if any in each of the above compounds B Methane generating bacteria methanogens thrive in the airless muck at the bottom of swamps As energy sources they can use hydrogen or metallic iron found in certain rocks The reaction is 8H aq 4Fe s CO 2 g CH 4 g 4Fe2 aq 2H2O l G 136 kJ at 25 C 1 atm pH 7 a What is E for this process b Rotten vegetation in swamps is usually acidic What is E for the above reaction at pH 5 when the partial pressures of CH4 and CO2 are each 0 1 atm and the concentration of Fe2 is 0 01 M Note that the reference state pH is 7 c Is the forward reaction more or less favorable under acidic conditions Briefly state your reasoning