Q5 The standard cell potential (E°) of a voltaic cell constructed using the cell

Question

Q5

The standard cell potential (E°) of a voltaic cell constructed using the cell reaction below is 0.76 V:

Zn(s) + 2H+(aq) Zn2+(aq) + H2(g)

With PH2 = 1.0 atm and [Zn2+] = 1.0 M, the cell potential is 0.66 V. The concentration of H+ in the cathode compartment is ________ M.

The standard cell potential (E°) of a voltaic cell constructed using the cell reaction below is 0.76 V:

Zn(s) + 2H+(aq) Zn2+(aq) + H2(g)

With PH2 = 1.0 atm and [Zn2+] = 1.0 M, the cell potential is 0.66 V. The concentration of H+ in the cathode compartment is ________ M.

Explanation / Answer

E0cell= 0.76V

Ecell=0.66V

PH2= 1.0 atm

[Zn+2] = 1.0M   n= 2e-

Ecell = E0cell - 0.059/n log[Zn+2]xPH2/[H+]^2

0.66 = 0.76- 0.059/2 log1.0x1.0/[H+]^2

- 0.1 = -0.059/2 x log1.0x1.0/[H+]^2

3.39 = log1/[H+]^2

1/[H+]^2 = 10^3.39

1[H+]^2= 2454.71

[H+]^2 = 1/2454.71 = 4.073 x10^-4

[H+] = 2.018 x10^-2

[H+] = 2.0 x10^-2M

The answer is A.

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