electrochemsumadv07 - AP Chemistry Electrochemistry Summary...

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AP ChemistryElectrochemistry Summary InformationElectrochemistrydeals with: a.using chemical reactions to do work (i.e. provide electricity) (known as voltaicor galvanic cells).b.using electricity to force nonspontaneous reactions (known as electrolyticcells).Voltaic Cells:Recall that oxidation-reduction(redox) reactions involve the transfer of electrons from one chemical to another.Ex.Mg + Cl2MgClIn this example magnesium loses two electronsMg0Mg2++ 2e-and is considered oxidizedEach chlorine gains an electronCl20+ 2e-2Cl-and is considered reducedThings to remember:Redox reactions always occur in pairsThe charge on any element is zero.The species being reduced is the oxidizing agent: The species being oxidized is the reducing agent.Remember the saying: LEOgoes GERLoses Electrons OxidizedGains Electrons ReducedQuestion:Determine which element is oxidized and which is reduced in the following reactions:1.2AgNO3+ Cu 2Ag + Cu(NO32.F2+ 2NaCl Cl2+ 2NaF2)2Answers: Silver is reduced (1+0), copper is oxidized (0 2+); Fluorine is reduced (0 1-), chlorine is oxidized (1-0).A more “active” metal will reduce a less active metal (since the more active metal has a greater tendency to lose electrons. Also, in general, most metals will reduce most nonmetals. An activity serieslists metals from more active to less active as in the following:Li, K, Ba, Ca, Na, Mg, Al, Zn, Fe, Cd, Ni, Sn, Pb, Cu, Hg, Ag, AuIn other words, lithium is the most active metal in this list and can therefore reduce the ion of any of the metals that come after it in the series. (ex. 3Li + Al3+3Li1++ By separating the oxidation part of a reaction from the reduction part then connecting them by a wire, useful work can be done. As electrons flow from the oxidation side to the reduction side they can pass through a light bulb, motor, etc., providing power to make them run. This type of setup is known as a voltaic(or galvanic) cellThe difference in potential energy between the two sides (relative to hydrogen) is known as the potential difference and is measured in Volts (J/C). For instance, the reaction between a silver ion and aluminum metal is 2.46V.
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