Determine the overall cell reaction and E degree_cell (at 25 degree C) of a Zn e

Question

Determine the overall cell reaction and E degree_cell (at 25 degree C) of a Zn electrode in a 1.0 M Zn(NO 3)_2 solution and a Cd electrode in a 1.0 M Cd(NO_3)_2 solution. E degree (Zn^2+/Zn) = -0.76 V, E degree (Cd^2+/Cd) = -0.40 V. What reaction occurs in the cell? A. Zn(s) + 2H^+ (aq) rightarrow Zn^2+ (aq) + H_2(g) B. Zn^2+ (aq) + Cd(s) rightarrow Zn(s) + Cd^2+ (aq) C. Cd^2+ (aq) + Zn^2+ (aq) rightarrow Cd(s) + Zn(s) D. Cd^2+ (aq) + Zn(s) rightarrow Cd(s) + Zn^2+ (aq) Calculate the E degree_cell. E degree_cell = V

Explanation / Answer

Solution:- First of all let's write the reduction equations for both the electrodes...

Zn2+(aq) + 2e-  -----> Zn(s) E0 = -0.76 V

Cd2+(aq) + 2e-  -----> Cd(s)   E0 = -0.40 V

More negative or less positive is the standard reduction potential, higher is the tendency to get oxidized. Since the standard reduction potential of Zn electrode is more negative so oxidation of zink and reduction of cadmium would take place. The over all cell reaction is will be...

Cd2+(aq) + Zn(s) -----> Cd(s) +  Zn2+(aq)

So, the correct choice is D.

E0cell = E0(cathode) - E0(anode)

we know that reduction takes place at cathode and oxidation at anode.So,.....

E0cell = -0.40 V - (-0.76 V)

E0cell = -0.40 V + 0.76 V

E0cell = +0.36 V

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