And products are in standard states can be computed

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oWhat is the maximum electrical work done by the cell on its surroundings during this experiment?Max work produced = -welec,max = -welec,rev = +1903 JCell PotentialoElectrons are “driven” from anode to cathode by electromotive force (emf) (change in potential)oFor Zn/Cu cell, this is indicated by voltage of 1.10 V at 25*C and when [Zn2+] and [Cu2+] = 1.0 M oInsead of tabulating potential for every possible electrochemical cell, half reactionpotentials are tabulatedoBalane half reactions can be added together to get overall balanced equation; if we know E* for each half reaction, we could get E* for net reactionoCan’t measure ½ reaction E* directly. Therefore, measure it relative to a standard hydrogen Electrode, SHE, also NHE (normal hydrogen electrode)2H_(aq, 1M) + 2e- 00> H2(g, 1 atm); this E* = 0.0 V is set to zero, everything else is in relation to this reactionoZn/Zn2+ half cell hooked to a SHE. ΔE* measured for the cell is +.76 VNet reaction: Zn(s) + 2H+ Zn2+ + H2(g)2/3/16Electrons are “driven” from anode to cathode by an electromotive force or emf (change inpotential)oFor Zn/Cu cell, this is indicated by a voltage of 1.10 V at 25*C and when [Zn2+] and [Cu2+] = 1.0 MCu2+ + Zn Cu + Zn2+Difficult to measure each cell for every single combinationCell potentialoInstead of tabulating the potential for every possible electrochemical cell, half reaction potentials are tabulatedoBalanced half reactiosn can be added together to get overall, balanced equationoZn(s) … Ex. Zn/Zn2+ half-cell hooked to a SHE. ΔE* measured for the cell: +0.76 VoOverall reaction is sum of two half reactions: Cathode: 2H+ (aq) + 2e- H2(g)Anode: Zn(s) Zn2+(aq) + 2e-So overall potential is ΔE* (cell) = e*)cahode) – E*(anode) +0.76 V = 0.00 V – E* (anode)half reaction potential Zn Zn2+(aq) + 2e- is +0.76 V
standard reduction potential: Zn2+(aq) + 2e- Zn is -.76 VCu2+/Cu and 2H+/H2 celloΔE*(cell) = +.34 VThis electrochemical cell runs right to left (cu is the cathode, hydrogen is the anode) So if you do the overall reaction as sum fo two half reactions: Half reaction potential and standard reduction potential is +.34 V for Cu2++ 2e- CuZn2+/Zn and Cu2+/Cu celloAnode, negative source of electrons (zinc)oCathode (positive, sink for electrions)Anode: zinc… E* = -.76 VCathode: copper… E* = +.34 VOverall potneial is ΔE*(cell) = E* (cathode) – E*(anode)= +.34 V – (-0.76 V) = +1.10 Vtable of standard reduction potentialsobest oxidizing agents at top left (reduction potential is higher) oany substance on the right will reduce any substance higher than it on the leftZn can reduce H+ and Cu2+

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