Electrochemistry – Research Projects 2 or 3 PowerPoint slides May use my background Font - size 18 or 20 Tahoma I have access to pictures in the book – just ask for them. Sample questions to answer What it is? How does it work? How is it related to electrochemistry? Include in slides Diagram(s) Half reactions or cells balanced equations Due Date 11/13 Five minute (NO LONGER) presentation. Topics: Lead Storage Batteries 17.5 Dry Cell Batteries 17.5 Fuel Cells 17.5 NiCd Batteries 17.5 Photovoltaic cells 17.5 Galvanizing 17.6 Cathodic Protection 17.6 Hall Heroult Process 17.8 Electrorefining 17.8 e-

Introduction to Batteries and Corrosion Electrochemistry Introduction to Batteries and Corrosion Chapter 17 Sections 5 & 6 e-

Electrochemistry- Batteries A galvanic cell or group of galvanic cells connected in series Potentials of individual cells = total battery potential Direct current Series vs. Parallell e-

Electrochemistry- Batteries How are these connected? Series Two 1.5V , 2000mAH in series = 3.0V & 2000mAH Parallel Two 1.5V, 2000mAH in parallel = 1.5V & 4000mAH What is going on here? Four batteries, two pairs in series, pairs connected in parallel 3.0V & 4000mAH e- http://itp.nyu.edu/physcomp/Notes/Batteries

Electrochemistry- Corrosion Corrosion returns metals to their natural states, ores. Oxidation of metal Metals that are easily corroded have reduction potentials less than O2 (g) Most metals develop a thin oxide coating – preventing further oxidation Al E = -1.7V thin layer of Al2O3 or Al2(OH)6 E = -0.6 V Fe forms a rust coating but it flakes off exposing more iron Cu forms CuCO3 or green patina Ag forms Ag2S or tarnish e-

Electrochemistry- Corrosion Corrosion Mechanism of Steel Steel has a non-uniform surface – not completely homogeneous Anions, Fe2+, flow through the moisture to the cathode to react with oxygen gas The moisture is the salt bridge; the metal is the “wire” for e- flow. Fe2+ (aq) + O2 (g) + (4n+2n) H2O(l)  2Fe2O3•n H2O(s) + 8H+(aq) Different degrees of hydration produces various FexOy compounds with various colors – red, black yellow e- p. .814

Electrochemistry- Corrosion Corrosion Mechanism of Steel NaCl or any salt accelerates corrosion The salt dissolves in the moisture which increases conductivity Cl1- forms many stable complexes with Fe3+ e- p. .814