Consider a galvanic cell based in the reaction Fe 2+ + Cr 2 O 7 2 - $\to$Fe 3+ + Cr 3+ in acidic solution.
-Calculate the voltage of the standard cell carrying out this reaction.

Question

Quizplus · Accepted Answer

The first step to calculate the standard cell voltage is to write the balanced equation and determine the standard reduction potentials for each half-reaction. Using a standard reduction potential table, we find:

Fe3+ + e- → Fe2+        E° = 0.77 V
Cr2O72- + 14H+ + 6e- → 2Cr3+ + 7H2O      E° = 1.33 V

Next, we need to flip the oxidation half-reaction and multiply it so that the number of electrons equalizes with the reduction half-reaction:

6Fe2+ → 6Fe3+ + 6e-
Cr → Cr3+ + 3e-

Then, we add the two half-reactions to get the overall balanced equation:
6Fe2+ + Cr → 6Fe3+ + Cr3+

We can now use the Nernst equation to calculate the standard cell voltage:

Ecell = E°cell - (RT/nF)lnQ

where E°cell is the standard cell potential, R is the gas constant, T is the temperature, n is the number of moles of electrons transferred, F is the Faraday constant, and Q is the reaction quotient, which is equal to the ratio of the product concentrations over the reactant concentrations, each raised to their stoichiometric coefficients.

Since the cell is operating under standard conditions, Q = 1 and the equation simplifies to:

Ecell = E°cell

Substituting the values of the standard reduction potentials, we get:

E°cell = Ecathode - Eanode
E°cell = (1.33 V) - (0.77 V)
E°cell = 0.56 V

Therefore, the answer is D) 0.56 V.

Consider a Galvanic Cell Based in the Reaction Fe2+ →\to→ Fe3+ + Cr3+ in Acidic Solution

Consider a Galvanic Cell Based in the Reaction Fe²⁺ $\to$ Fe³⁺ + Cr³⁺ in Acidic Solution