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 degreeC and 1 M To calculate the cell potential at non-standard-state conditions, one uses the Nernst equation. E = E^o - 2.303 RT/nF log_10 Q where E is the potential in volts, En is the standard potential in volts. R = 8.314 J/(K. 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^o - 0.592/n log_10 Q PartE What is the cell potential for the reaction Mg(s) + Fe^2+ (aq)rightarrowMg^2+ (aq) + Fe(s) at 55 degreeC when [Fe^2+ ] = 3.80 M and [Mg^2+] = 0.210 M. Express your answer to three significant figures and include the appropriate units.

Explanation / Answer

According to nernest equation

E = E0 - 0.059/n log{[oxidised]/[reduced]}

E0cell= E0cathode - E0anode = -0.44 - (-2.37) = 1.93v

n = 2e-( no. of electrons change in redox reaction)

E = 1.93 - (0.059/2) log(0.210/3.80)

E = 1.93 -(0.059/2)*(-1.26)

E = 1.97 V

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