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Consider the following relations for emf of an electrochemical cell
(a) emf of cell = (Oxidation potential of anode) – (Reduction potential of cathode)
(b) emf of cell = (Oxidation potential of anode) + (Reduction potential of cathode)
(c) emf of cell = (Reduction potential of anode) + (Reduction potential of cathode)
(d) emf of cell = (Oxidation potential of anode) – (Oxidation potential of cathode)
Which of the above relations are correct?
(a) emf of cell = (Oxidation potential of anode) – (Reduction potential of cathode)
(b) emf of cell = (Oxidation potential of anode) + (Reduction potential of cathode)
(c) emf of cell = (Reduction potential of anode) + (Reduction potential of cathode)
(d) emf of cell = (Oxidation potential of anode) – (Oxidation potential of cathode)
Which of the above relations are correct?
A
(c) and (a)
B
(a) and (b)
C
(c) and (d)
D
(b) and (d)
Detailed Solution
The basic relation is: $E_{cell} = E_{cathode}(\text{reduction}) - E_{anode}(\text{reduction})$
Oxidation potential of an electrode = −(its reduction potential).
Replacing the anode term: $-E_{anode}(\text{red}) = +E_{anode}(\text{oxid})$, so $E_{cell} = E_{anode}(\text{oxid}) + E_{cathode}(\text{red})$. This is relation (b).
Replacing the cathode term as well: $E_{cathode}(\text{red}) = -E_{cathode}(\text{oxid})$, so $E_{cell} = E_{anode}(\text{oxid}) - E_{cathode}(\text{oxid})$. This is relation (d).
Relations (a) and (c) have the wrong signs.
Hence the correct relations are (b) and (d).
Oxidation potential of an electrode = −(its reduction potential).
Replacing the anode term: $-E_{anode}(\text{red}) = +E_{anode}(\text{oxid})$, so $E_{cell} = E_{anode}(\text{oxid}) + E_{cathode}(\text{red})$. This is relation (b).
Replacing the cathode term as well: $E_{cathode}(\text{red}) = -E_{cathode}(\text{oxid})$, so $E_{cell} = E_{anode}(\text{oxid}) - E_{cathode}(\text{oxid})$. This is relation (d).
Relations (a) and (c) have the wrong signs.
Hence the correct relations are (b) and (d).