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 model for such a concentration cell involving a metal M is:
molar molar
For the above electrolytic cell the magnitude of the cell potential .
If the 0.05 molar solution of is replaced by a 0.0025 molar solution, then the magnitude of the cell potential would be
molar molar
For the above electrolytic cell the magnitude of the cell potential .
If the 0.05 molar solution of is replaced by a 0.0025 molar solution, then the magnitude of the cell potential would be
- (A)35 mV
- (B)70 mV
- (C)140 mV✓ Correct
- (D)700 mV
Answer: (C)
Solution
From the Nernst equation for the original cell:
This gives:
For the new concentration:
Alternatively, note that the concentration decreased by a factor of 20 (from 0.05 to 0.0025), which adds approximately to the original 70 mV, giving 140 mV.
This gives:
For the new concentration:
Alternatively, note that the concentration decreased by a factor of 20 (from 0.05 to 0.0025), which adds approximately to the original 70 mV, giving 140 mV.
JEE Advanced · 2010 · 11 Apr 2010 · Paper 1 · Single correct option