The concentration of potassium ions inside a biological cell is at least 20 times higher than outside. The resulting potential difference across the cell is important in several processes such as transmission of nerve impulses and maintaining the ion balance. A simplel model for a concentration cell involving a metal `M` is
`M(s)|M^(o+)(aq,0.05 ` molar`)||M^(o+)(aq,1` molar`)|M(s)`
For the abov electrolytic cell, the magnitude of the cell potential is `|E_(cell)|=70mV.`
If the `0.05` moolar solution of `M^(o+)` is replaced by a `0.0025` molar `M^(o+)` solution, then the magnitude of the cell potential would be

Options

A. 35 mV
B. 70 mV
C. 140 mV
D. 700 mV

Answer

C

Explanation

1. (b) Electrolyte concentration cell will be spontaneous when the concentration in cathodic half cell is greater than that of anodic half cell. Thus, the given cell is spontaneous hence
`DeltaG lt 0, E_(cell) gt 0`
2. (c) `E_(cell)^(@)=0`, for every concentration cell
`E=0-0.059/n"log"([M^(+)]_("anode"))/([M^(+)]_("cathode"))`
`=-0.059/1log[0.0025]=+153 mV`
It is close to 140 mV.