1.) What is the potential of an electrochemical cell made from the Zn/Zn 2+ and

Question

1.) What is the potential of an electrochemical cell made from the Zn/Zn2+ and Cu/Cu2+ half cells under standard conditions?

E. Cannot be determined because no reference is made to the Standard Hydrogen Electrode (SHE) in the problem as worded.

A. + 1.10 V B. - 1.10 V C. + 0.42 V D. - 0.42 V

E. Cannot be determined because no reference is made to the Standard Hydrogen Electrode (SHE) in the problem as worded.

2.) Calculate the value of Keq at 25°C for the reaction:

    Cu2+(1.00M) +   Fe(s)     Cu(s) +   Fe2+(1.00M)

A. 2.4 x 10-26 B. 60.7 C. 4.2 x 10–27 D. 2.4 x 1026 E. 4.2 x 1027

Explanation / Answer

1) E0cell = E0cathode -E0anode

E0 Zn2+/Zn = -0.762 v

E0 Cu2+/Cu = +0.337 v

E0cell = 0.337 - (-0.762)

   = 1.1 v

answer: A

2) E0cell = E0cathode - E0anode

E0cathode = Cu^2+/Cu = +0.337 V

E0anode = Fe^2+/Fe = -0.44 V

E0cell = 0.337 - (-0.44)

       = 0.777 V

DG0 = - nFE0cell

n = no of electrons transfered = 2

F = 96500 c

E0 = 0.777 V

= -2*96500*0.777

DG0 = - 149.961 kj

DG0 = - RTlnk

-149961 = -8.314*298lnk

   k = 2*10^26

answer: D

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