Using the Nernst Equation: To learn how to use the Nernst equation. The standard

Question

Using the Nernst Equation:

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 ?C and 1 M. To calculate the cell potential at non-standard-state conditions, one uses the Nernst equation,

E=E??2.303RTnFlog10Q

where E is the potential in volts, E? is the standard potential in volts, R=8.314J/(K?mol) is the gas constant, T is the temperature in kelvins, n is the number of moles of electrons transferred,F=96,500C/(mol e?) is the Faraday constant, and Q is the reaction quotient.

Substituting each constant into the equation the result is

E=E??0.0592 Vnlog10Q

Part E What is the cell potential for the reaction the reaction Mgs) Mg(s) + Fe2+ (aq) Mg2 + (aq) + Fe(s) Express your answer to three significant figures and include the appropriate units 2 EValueUnits Submit Hints My Answers Give Up Review Part

Explanation / Answer

The reaction is

Mg(s) + Fe+2 ------------> Mg+2 +Fe

Mg -------. Mg+2 +2e-    Eo= 2.37 V and Fe+2+2e- -----------> Fe   Eo=-0.44V

when added , the above reactions give Mg +Fe+2--------> Mg+2 +Fe Eo= 2.37-0.44= 1.93 V

n= 2 electrons , Eo=1.93 V, R= 8.314 Joules/mole.K T= 87+273.15 K=360.15 K, F= 96500 coulumb/moles

Q= Reaction coefficient = [Mg+2]/ [Fe+2] = 0.31/3.5=0.089

E= 1.93- 2.303*8.314* 360.15/2*96500) log (0.089)=1.93+0.038=2.008V

Related Questions

Navigate

• Browse (All)
• Browse U
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.