Free-energy change. Delta G degree. is related to cell potential. E degree. by t

Question

Free-energy change. Delta G degree. is related to cell potential. E degree. by the equation Delta G degree = -n FE degree where n is the number of motes of electrons transferred and F = 96, 500 C/(mol e^-) is the Faraday constant. When E degree is measured in volts and can be determined from half-reaction potentials as given in the table below. Delta G degree must be in joules since 1 J = 1 C middot V. Calculate the standard free-energy change at 25 degree C for the following reaction using the table in the introduction: Mg(s) + Fe^2+ (aq) rightarrow Mg^2+ (aq) + Fe(s) Express your answer numerically in joules. Calculate the standard cell potential at 25 degree C for the reaction X(s) + 2Y^+(aq) rightarrow X^2+(aq) + 2Y(s) where Delta H degree = -809 kJ and Delta S degree = -381 J/K. Express your answer numerically in volts.

Explanation / Answer

A)
Eo (Mg2+/Mg) = -2.37 V
Eo (Fe2+/Fe) = -0.45 V

number of electron being transferred, n=2
Eo cell = Eo cathode - Eo anode
               = -0.45 - (-2.37)
               = 1.92 V

Go = -n*F*Eo
          = -2*96500*1.92
          = - 370560 J
Answer: - 370560 J

B)
T = 25 oC = (25 +273) K = 298 K
Go = Ho - T*So
          = -809000 J - 298*(-381) J
          = -695462 J

number of electron being transferred, n=2

Go = -n*F*Eo
-695462 = -2*96500*Eo
Eo = 3.60 V
Answer: 3.60 V

Related Questions

Navigate

• Browse (All)
• Browse F
• Subjects

---

---

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