Write the Nernst equation and the emf of the following cell at 298K:
Mg(s)/Mg2+(0.001M) ∕∕ Cu2+(0.0001M) ∕ Cu(s)
Given, E0Mg2+/Mg = -2.37 V; E0Cu2+/Cu = + 0.34 V
Answers
Explanation:
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Answer: Emf of the cell = 2.68 V
Explanation:
Chemical equation involved for above cell is
Mg + Cu2+ ------> Mg2+ + Cu
from above
Cathode rxn : Cu2+ ----> Cu
Anode rxn : Mg -----> Mg2+
Nernst eqn at 298 K
Ecell = E°cell -.0591/n ×log[p]/[r]
( p= product , r= reactant )
Here , n = 2 ( loss and gain of 2 electrons in the above cell reaction )
Nernst equation for above cell
Ecell = E°cell -0.0591/2 × log [Mg2+][Cu]/ [Mg][Cu2+] .......1
E°cell = E°cathode - E°anode
E° Cu2+/Cu - E° Mg2+/Mg
+0.34 – (– 2.37) V
= 2.71 V
Substituting the values in equations (1)
Ecell = 2.71 – 0.0591/2×log [0.001][ 1] / [1][0.0001]
after calculating, and taking log10=1
Ecell = 2.68 V (approx)