A) A half-cell that consists of a copper wire in 1.00 M CuNO 3 solution is conne

Question

A) A half-cell that consists of a copper wire in 1.00 M CuNO3 solution is connected by a salt bridge to a half cell containing a 1.00 M X(II) acetate solution and an electrode of metal X. The voltage of the cell is 0.28 V, with metal X as the positive electrode. Calculate the standard reduction potential for the X half-reaction. The standard reduction potential of the copper half-reaction is 0.52 V. (Hint, write the half-reactions and the overall chemical equation for the spontaneous reaction.)

B) Calculate ?Go (in J) for 2 moles of electron(s) in each half-reaction and a standard potential of 0.46 V.

Explanation / Answer

(A) Reduction at cathode (positive electrode): X2+ + 2 e- => X

Oxidation at anode (negative electrode): Cu => Cu+ + e-

Overall cell reaction: 2 Cu + X2+ => 2 Cu+ + X

Eo(cell) = Eo(X2+/X) - Eo(Cu+/Cu)

0.28 = Eo(X2+/X) - 0.52

Eo(X2+/X) = 0.80 V

(B) Moles of electrons n = 2

Faraday constant F = 96485 C/mol

Eo(cell) = 0.46 V

Delta Go = -nFEo(cell)

= -2 x 96485 x 0.46

= -8.88 x 10^4 J/mol = -88.8 kJ/mol = -89 kJ/mol

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