Question

The concentration of potassium ions inside a biological cell is at least twenty times higher than the 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 simple mode for such a concentration cell involving a metal `M` is :
`M_((s))|M_((aq.))^(@) 0.05"molar"||M_((aq.))^(@) 1"molar"|M_((s))`
For the above electrolytic cell the magnitude of the cell potential `|E_(cell) | = 70mV`
For the above cell :
A. `E_(cell)lt0,DeltaGgt0`
B. `E_(cell)gt0,Deltalt0`
C. `E_(cell)lt0,DeltaH^(@)gt0`
D. `E_(cell)gt0,DeltaG^(@)gt0`

Answer 1

Correct Answer - B
It is an electrolyte concentration cell in which the electrode with concentrated electrolyte solution acts as cathode and second one as anode. For a concentration cell, appling Nernst s equation,
`E_(cell)=(0.059)/(n)log.([M_("aq..")^(n+)]_("Cathode"))/([M_("aq..")^(n+)]_("anode"))`
`E_(cell)=(0.056)/(0.1)log_(10).([1.0])/(5xx10^(-2))`
`=0.076or76mV`(i.e.,positive value)
Also `DeltaG=-2FE`, because E is positive so `DeltaGlt0`.