Q4(b). Standard and actual potential of the Cu / Fe³⁺, Fe²⁺ cell
Consider a galvanic cell that uses the reaction
Cu(s) + 2Fe³⁺(aq) → 2Fe²⁺(aq) + Cu²⁺(aq)
Given, E°(Fe³⁺/Fe²⁺)=+0.77 V and E°(Cu²⁺/Cu)=+0.34 V.
(i) Calculate the standard cell potential.
(ii) Obtain the cell potential at 25°C that has the following concentration values:
[Fe³⁺]=1.0×10⁻⁴ M; [Cu²⁺]=0.25 M; [Fe²⁺]=0.2 M
(Given, F=96500 C, R=8.314 J K⁻¹ mol⁻¹)
Answer in brief
(i) E°cell=+0.43 V. (ii) Q=1.0×10⁶, Ecell=0.43-0.1774=0.253 V; still positive, so the reaction remains spontaneous.
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All parts of Question 4
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- 4(a)(ii) Surface area of silica gel from the nitrogen monolayer10 marks
- 4(b) Standard and actual potential of the Cu / Fe³⁺, Fe²⁺ cell10 marks
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