Completed+notes+for+ch+19++electrochem+

Completed+notes+for+ch+19++electrochem+ - Chapter 19 -...

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Unformatted text preview: Chapter 19 - ELECTROCHEMISTRY The principles of electrochemistry affect your everyday life: Batteries (cell phone, laptop, etc) Metal corrosion (your car) lon-selective meters (biological sensors, pH meter) Officially, ELECTROCHEMISTRY is the study of the interchange of chemical and electrical energy. We will mostly be focusing on oxidation/reduction reactions. These are the flow of electrons from one species to another. These reactions can be spontaneous and generate an electrical current (electrons flowing is a current) We can "electroplate" ions onto a surface, resulting in a nice, clean metal surface. OXI DATION/R EDUCTION REACTIONS Oxidation - loss of electrons as the reaction progresses: A _-..-\ ALr r Lc' C {olr oo L oler{.0^r) Reduction - gain of electrons as the reaction progresses: At* r le- -t A C5.,i,r o{ Z +leof,*r J These will ALWAYS happen in tandem reduction is also occurring somewhere- if oxidation occurs then else in the reaction. Two methods of remembering the differences between oxidation and reduction: 1) lf the oxidation state of an atom in a molecule gets smaller, or is reduced, than that molecule is undergoing reduction. lf the oxidation state gets bigger, oxidation is occurring. 2) The simple pneumonic device "OlL RlG": ! L ( T. C, The oxidation state of something relates the number of electrons either owned or shared unequally in that atom's valence shell. lf after a reaction more electrons are around, or gained, the oxidation state will be lower (more negative) than it was initially. lf after a reaction fewer electrons are around, the oxidation state will be higher (more positive) than it was initially. O xg oArfov s os5 E Oqc t lorv I As u r gfer> h ^^ ele"+r$-\ To further confuse things, we also like to discuss the agents of oxidation and reduction: Oxidation aoent - the species in the reaction which oxidizes another reagent by taking electrons away. Reduction aqent - the species in the reaction which reduces another reagent by giving electrons to it. These are initially confusing, but because oxidation/reduction reactions always happen in pairs, determining the agents of oxidation and reduction becomes fairly simple: lf something is the reducing agent, it has given electrons to another reactant, thus has experienced a loss of electrons and is oxidized. lf something is the oxidation agent, it is taking electrons away from another reagent, thus gaining electrons itself, being reduced in the reaction. The species oxidized in an electrochemical reaction is the reducing agent, and the species reduced is the oxidation agent. You can picture this in terms of someone being mugged for their electrons: d v A--c'J'-- 3 rl') r tt.r tr,A 5r rr o*i,lq,Tit'^'t56at" Jh o,r;d,itd 5t e'{'lrl " r a4"rc L^, ,\1?rr{ t' g !ct)n t For the foltowing reactions, balance, determine what is oxidized, reduced and what is the oxidation and reduction agent. Write the hatf-reactions that describe the oxidation and reduction....
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Completed+notes+for+ch+19++electrochem+ - Chapter 19 -...

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