For the cell: Cr | Cr^3+ || Co^2+ | Co E degree is 0.46 V. The same cell was pre
ID: 963770 • Letter: F
Question
For the cell: Cr | Cr^3+ || Co^2+ | Co E degree is 0.46 V. The same cell was prepared in the laboratory at standard conditions. The voltage obtained was 0.40 V. A possible explanation for the difference is the surface area of the chromium electrode was smaller than the cobalt electrode. the mass of the chromium electrode was larger than the mass of the cobalt electrode. the concentration of Co(NO_3)_2 solution used was less than 1.0 M. the concentration of Cr(NO_3)_2 solution used was less than 1.0 M. the volume of Co(N03)2 solution used was larger than the volume of Cr(NO_3)_2 solution used.Explanation / Answer
The cell potential can be calculated form Nernst equation which is
E(cell) = E0(cell) - (0.0591 / n) x log ([Co2+] / [Cr3+])
=> 0.40 V = 0.46 V - (0.0591 / n) x log ([Co2+] / [Cr3+])
=> (0.0591 / n) x log ([Co2+] / [Cr3+]) = 0.06 V > 0
This is possible only when the concentration of Cr3+ or Cr(NO3)3 solution used was less than 1.0 M