Thanks Q. An electrochemical cell, composed of an iron electrode (anode) immerse
ID: 1049748 • Letter: T
Question
Thanks Q. An electrochemical cell, composed of an iron electrode (anode) immersed in 0.10 M Fe(NO3)2 and a silver electrode (cathode) immersed in 0.11 M AgNO3, was found to have a cell potential of 1.21 V. The standard reduction potential for the Ag+/Ag half-cell is +0.80 V. The standard reaction potential for the Fe2+/Fe half-cell is -0.45 V.a) write the half cell reaction at the anode.
b) write the half cell reaction at the cathode.
c) write the overall cell reaction.
d) Determine the standard cell potential( ) using the standard reduction potentials given above.
e) Determine the standard cell potential ( ) using the Nernst equation.
electrode and identify the anode for each electrochemical cell. Remember that the cell potential should be a positive value. Determine Standard Potentials Using Literature Values. First, write the cathode half-reaction, anode half-reaction and the overall cell reaction for each cell. Then, using standard reduction potentials from the literature, determine the standard potential (AEo) for each cell according to the following equation. Oxidation occurs at the anode and reduction occurs at the cathode. Remember that E for an oxidation potential is the negative of E° for a reduction potential. An electrical potential does not depend on how much reaction occurs; therefore, do not multiply E the coefficient from the balanced equation. o by Determine Standard Potentials Using the Nernst Equation. Use the Nernst equation to determine standard potentials (e) from the measured potential values (e) for each cell. To determine standard potentials from actual potentials, rearrange the Nernst equation as follows: (at 25°C) e" = + 0.0591 V log [prodr [react.]
Explanation / Answer
The standard electrode potential for Fe system is Fe2+ + 2e- -----> Fe ; Eo red = -0.45 V ---(1)
The standard electrode potential for Ag system is Ag+ + e- ------> Ag ; Eo red = +0.80 V ---(2)
Since the reduction potential of Fe system is less it undergoes oxidation at anode & Ag undergoes reduction at cathode.
The cell reaction is Fe + Ag+ -----> Fe2+ + Ag
So standard potential of the cell , Eo = Eocathode - Eoanode
= EoAg+/Ag - EoFe2+/Fe
= +0.80-(-0.45)
= +1.25 V
According to Nernst Equation ,
E = Eo - (0.059 / n) log ([Products] / [reactants] )
= Eo - (0.059 / n) log ([Fe2+] / [Ag+] )
Where
E = electrode potential of the cell = ?
Eo = standard electrode potential = +1.21 V
n = number of electrons involved in the reaction = 2
[Ag+] = 0.15 M
[Fe2+] = 0.101M
Also
Plug the values we get
E = Eo - (0.059 / n) log ([Fe2+] / [Ag+] )
= +1.21 - (0.059 / 2 ) x log ( 0.10 / 0.15 )
= +1.215 V
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