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(Solution document) cant seem to wrap my head around these final two questions, I got the first parts but im stuck on the rest can someone explain to me how to solve it?...


I just cant seem to wrap my head around these final two questions, I got the first parts but im stuck on the rest can someone explain to me how to solve it?


1. Reference Electrodes


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

Ag2CrO4(s) + 2e- --> 2Ag(s) + CrO42-(aq)

A chemist wishes to determine the concentration of CrO42- 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 CrO42- solution.


a) What is the potential of this cell at 25°C when [CrO42-] = 1.00 M?

0.204 V


b) Calculate ?G for the full-cell reaction at 25°C when [CrO42-] = 1.00 M?

-3.94×101 kJ


c) What is the potential of this cell at 25°C when [CrO42-] = 9.90×10-9 M?


d) For a solution of unknown [CrO42-], the measured potential for the cell at 25°C is 0.327 V. What is [CrO42-] (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.)

 







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