To learn how to use the Nernst equation. The standard reduction potentials liste

Question

To learn how to use the Nernst equation. The standard reduction potentials listed in any reference table are only valid at standard-state conditions of 25 degree C and 1 M. To calculate the cell potential at non-standard-state conditions, one uses the Nernst equation. E = E degree - 2.303 RT/nF log_10 Q where E is the potential in volts, E degree is the standard potential in volts, R = 8.314 J/(K middot mol) is the gas constant, T is 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 E = E degree - 0.0592 v/n log_10 Q Consider the reaction Mg(s) + Fe^2+ (aq) rightarrow Mg^2+ (aq) + Fe(s) at 77 degree C, where [Fe^2+] = 3.40 M and [Mg^2+] = 0.310 M. What is the value for the reaction quotient, Q for the cell? What is the value for the temperature, T, in kelvins?

Explanation / Answer

products = Mg+2 and Fe, ignore Fe since solid (activity = 1)

reactants = Fe+2 and Mg(S) , ignore Mg so

Q = [products]/[Reactants]

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

Q = (0.31)/(3.40) = 0.091176

B)

T = T(°C) + 273 ) 77+273 = 350.0 K

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