Secondary reference electrodes with an anode/cathode problem? Would someone be a

Question

Secondary reference electrodes with an anode/cathode problem? Would someone be able to explain why (a) is the best answer? How do they calculate the Voltage?

7. The following electrochemical cell is used to determine the reduction potential of [Co(bpy)] at 25 °C, where bpy bipyridyl (shown below). The cell incorporates a Ag/AgCl secondary reference with saturated KCl that has a half-cell reduction potential of 0.20 V (Eanode ELHS 0.20 V) (a) The cell potential is measured to be 0.17 V. Calculate the reduction potential (F) for [Co(bpy)3]", (b) Explain why the experiment requires the presence of an excess concentration of 1 x 10 M of the bpy ligand. When this excess free ligand is absent the cell potential increases to 0.36 V Circle the most appropriate answer to this question: (A) (a) The reduction potential is 0.31 V. (b) An excess of the ligand is required so that  ' the complexes are fully formed. (B) (a) The reduction potential is 0.31 V. (b) An excess of the ligand stabilizes the [Co(bpy)3]2-complex over [Co(bpy)3]3. (C) (a) The reduction potential is 0.37 V. (b) An excess of the ligand stabilizes the [Co(bpy)3complex over [Co(bpy)3]2. (D) (a) The reduction potential is 0.37 V. (b) An excess of the ligand stabilizes the [Co(bpy)al2 complex over Co(bpy).

Explanation / Answer

Use the nerst equation:

E = E° - 0.059/n logQ

Q = 1x10-4 / 1x10-3 = 0.1

0.20+0.17 = 0.37
0.37 = E° - 0.059/1 log0.1
0.37 = E° + 0.059
E° = 0.37 - 0.059
E° = 0.31 V

That's why E° is 0.31 V. Now, for part b) of course is needed an excess because if not, the complex form would not be the 3+ charge.

Hope this helps

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.