Electrochemistry- using the Nernst Equation?
Given the half reactions:
Ce^(4+) + e− → Ce^(3+) E° = 1.72 V
Fe^(3+) + e− → Fe^(2+) E° = 0.771 V
What volume of 0.36 M Ce4+ solution must be mixed with 40. mL of 0.42 M Fe2+ solution to produce a solution which produces a platinum electrode potential (relative to SHE) of 1.2455 V.?
This is what I have so far:
I know E(cell) = E(cathode) - E(anode), or E(cell)= 1.72-.771 = 0.949 V
E= E(cell) - [0.0257/n]*ln(Q) [[where .0257 is a constant equal to RT/F at 298 K]]
1.2455= 0.949 - (0.0257/1)*ln(Q)
I can solve for the reaction quotient (Q), but I don't know how I'd solve for volume from that. Any help?
Answer:
Roughly ln(Q)= 11, and Q = 2.5
This means the molarity of the oxidized species is 2.5 time that of the reduced. You can figure the volume from algebra knowing:
( V * M)mix = SUM(V * M) components
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