t Introduction to the Nernst Equation Learning Goal: To learn how to use the Ner

Question

t Introduction to the Nernst Equation Learning Goal: To learn how to use the Nernst equation. The standard reduction potentials listed in an reference table are only valid at standard-state conditions of 25 C and 1 M. To calculate the cell potential at non-standard-state conditions, one uses the Nernst equation, 2.303 RT log10 Q nF where E is the potential in volts, E is the standard potential in volts, the temperature in kelvins, n is the number of moles of electrons transferred, F 96,500 C/(mol e is the Faraday constant, and Q is the reaction quotient. Substituting each constant into the equation the result is o 0.0592 V log10 Q

Explanation / Answer

A)

Q = [MG+2]/[Fe+2]

Q = (0.310)/(3.80 )

Q = 0.08157

B)

find T in K

T = 41C = 41+273 = 314 K

C)

find n, which is the number of moles of electrons transferred

Fe2+ = 2 electrons

Mg+2 = 2 electrons

then

n = 2 electrons are being transferred

D)

E° = Ered - Eox =

Fe2+(aq) + 2e– Fe(s) –0.44

Mg2+(aq) + 2e– Mg(s) –2.38

E° = -0.44 - -2.38

E° = 1.94 V

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