Postlab Questions Electrochemistry Name A voltaic cell consists of a FeFe\" half

Question

Postlab Questions Electrochemistry Name A voltaic cell consists of a FeFe" half-cell and a Cu/Cu2. half-cell at 25·C. The initial concentrations of Fe and Cu?' are 0.10 M and 0.50 M respectively. Standard reduction potentials are as follows: o.3 0.34 1. Which is the anode, which is the cathode? 2. What is the value of Ecell? 3. What is the value of Q, the reaction quotient, for this cell reaction? 4. How many electrons are transferred in the balanced reaction? 5. What is the cell potential at 25'C as read on the digital voltmeter(Ecel)?

Explanation / Answer

1) Iron , Fe+2/Fe is the anode , that is undergoes oxidation [negative SRP]

copper , Cu+2/Cu is the cathode, that is undergoes reduction.[positive SRP]

2) E0 cell = SRP of cathode - SRP of anode

= 0.34- (-0.41)

= 0.75V

3) The cell reaction is Fe + Cu+2 ----------> Fe+2 + CU

Thus Q = [FE+2]/[Cu+2]

=0.1/0.5= 0.2

4) In the balanced reaction Fe is oxidesed to Fe+2 by losing 2 electrons and

Cu+2 is reduced to Cu+2 by taking 2 electrons.

Thus the electrons transfered are 2.

5) Ecell is calcaulted according to Nernst equation

E cell = E0cell -[0.059/n] log Q

= 0.75V -0.059/2 log 0.2

=0.77V

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