Electrochemsitry

ElectrochemsitryRelationship between E, G, and K

Relation between Eo, Go, and K

G = Wmax amount of useful work done by a reaction system

For voltaic or galvanic cell, useful work is produced by the system.

-Wmax = QEQ = charge in coulombsE = voltagesoG = -QE

1 mole of electrons = 9.648x104 coulombs

so Q = (9.648x104 c/mol)(n)

G = -(9.648x104 c/mol)(n)(E)

G = -nFE or Go = -nFEo

remember that Go = -RTlnKRTlnK = nFEoEo = RTlnK/nF

at 25o C, RT/F = 0.0257 Vso Eo = (0.0257 V / n)lnK

orln K = nEo/0.0257

or log K = nEo/0.0592

Note that if Eo is +, Go is -, lnK is +, so K>1

Ex - Find Eo, Go, and K for Cl2(g) + 2 Br-(aq) 2 Cl-(aq) + Br2(l)

For solutions that are not at 1 M or 1 atm, we need the Nernst Equation.

In the expression for Q, gases enter as partial pressures in atmospheres and solutes as concentrations in molarity.

Ex - for the reactionCl2(g) + 2 Br-(aq) 2 Cl-(aq) + Br2(l)Calculate the voltage when [Br-] = 1 M, PCl2 = 1 atm and [Cl-] = 0.01 M

Nernst equation activity

Voltage goes up as expected - since the product concentration is low, the reaction should become more spontaneous toward the right.Ex - Consider the reactionZn(s) + 2 H+ Zn2+(aq) + H2(g)Suppose[Zn2+] = 1 M, PH2 = 1 atm, find [H+] and pH if the cell potential = 0.460 v.

Notes quizhttps://docs.google.com/spreadsheet/embeddedform?formkey=dGIwYVFjdHZVdE15a1FVdDlWM2JuQ2c6MQ