Reference no: EM131877736

1. Reference Electrodes

The E° value for the following reaction is 0.446 V relative to the standard hydrogen electrode (SHE):

Ag₂CrO₄(s) + 2e^- --> 2Ag(s) + CrO₄^2-(aq)

A chemist wishes to determine the concentration of CrO₄^2- electrochemically. A cell is constructed consisting of a saturated calomel electrode (SCE; which has a reduction potential of 0.242 V relative to the SHE) and a silver wire coated with Ag₂CrO₄ and suspended in a CrO₄^2- solution.

a) What is the potential of this cell at 25°C when [CrO₄^2-] = 1.00 M?

0.204 V

b) Calculate ΔG for the full-cell reaction at 25°C when [CrO₄^2-] = 1.00 M?

-3.94×10¹ kJ

c) What is the potential of this cell at 25°C when [CrO₄^2-] = 9.90×10^-9 M?

d) For a solution of unknown [CrO₄^2-], the measured potential for the cell at 25°C is 0.327 V. What is [CrO₄^2-] (in mol/L)?

2. Nernst Equation Applied to Half-Reactions

The Nernst equation can be applied to half-reactions.

a) Calculate the reduction potential (at 25°C) of the half-cell Cu/Cu²⁺ (2.8 M).

(The half-reaction is Cu²⁺ + 2e^- --> Cu.)

0.353 V

b) Calculate the reduction potential (at 25°C) of the half-cell MnO₄^- (1.50×10^-1 M)/ Mn²⁺ (2.30×10^-2 M) at pH = 2.00.

(The half-reaction is MnO₄^- + 8H⁺ + 5e^- --> Mn²⁺ + 4H₂O.)