3. A voltaic cell is constructed that uses the following reaction and operates a

Question

3. A voltaic cell is constructed that uses the following reaction and operates at 298 K.

(a) What is the emf of this cell under standard conditions?
_____V
(b) What is the emf of this cell when [Ni2+] = 3.49 M and [Zn2+] = 0.188 M?
_____V
(c) What is the emf of the cell when [Ni2+] = 0.185 M and [Zn2+] = 0.881 M?
_____V

4. A voltaic cell utilizes the following reaction and operates at 298 K.

(a) What is the emf of this cell under standard conditions?
____ V
(b) What is the emf of this cell when [Ce4+] = 1.6 M, [Ce3+] = 0.013 M, and [Cr3+] = 0.010 M?
____ V
(c) What is the emf of the cell when [Ce4+] = 0.59 M, [Ce3+] = 0.85 M, and [Cr3+] = 1.2 M?

____V

Explanation / Answer

3. For the given cell,

(a) emf of cell = -0.25 - (-0.763) = 0.513 V

(b) with the given concentrations,

Ecell = Eo - 0.0592/n logQ

         = 0.513 - 0.0592/2 log(0.188/3.49) = 0.550 V

(c) Ecell = Eo - 0.0592/n logQ

         = 0.513 - 0.0592/2 log(0.881/0.185) = 0.453 V

4. For the given cell,

(a) Eo = 1.61 - (-0.74) = 2.35 V

(b) with given concentrations,

Ecell = Eo - 0.0592/n logQ

         = 2.35 - 0.0592/3 log((0.013)^3 x (0.010)/(1.6)^3) = 2.513 V

(c) with given concentrations,

Ecell = Eo - 0.0592/n logQ

         = 2.35 - 0.0592/3 log((0.85)^3 x (1.2)/(0.59)^3) = 2.335 V

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