The standard cell potential (E°_cell)for the voltaic cell based on the reaction below is ________ V. Cr (s)+ 3Fe³⁺ (aq)→ 3Fe²⁺ (aq)+ Cr³⁺ (aq) A)-1.45 B)+2.99 C)+1.51 D)+3.05 E)+1.57

Question

Quizplus · Accepted Answer

The standard cell potential can be calculated using the formula: E°cell = E°reduction (cathode) - E°reduction (anode). We need to find the standard reduction potentials for each half-reaction and subtract them. The half-reactions are:
Cr3+(aq) + 3e- → Cr(s)..... E°reduction = -0.74 V
Fe3+(aq) + e- → Fe2+(aq)..... E°reduction = +0.77 V
S2O32-(aq) + 2e- → 2S2-(aq)..... E°reduction = -0.32 V
The reduction potential for the half-reaction involving Cr is negative and it is being oxidized while Fe and S are being reduced. Therefore, we need to flip the first half-reaction and change the sign of its reduction potential to get the oxidation potential.
Cr(s) → Cr3+(aq) + 3e-..... E°oxidation = +0.74 V
Now we can calculate the standard cell potential:
E°cell = E°reduction (cathode) - E°reduction (anode)
E°cell = (3 x E°reduction (Fe2+)) + E°reduction (S2-) - (E°oxidation (Cr))
E°cell = (3 x 0.77 V) + (-0.32 V) - 0.74 V
E°cell = 1.51 V
Therefore, the best choice is C: +1.51 V.

The Standard Cell Potential (E°cell)for the Voltaic Cell Based on the Reaction

The Standard Cell Potential (E°_cell)for the Voltaic Cell Based on the Reaction