IIT-JEE 2010 · Paper 1 · Chemistry Q17

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ChemistrySingle correct+3 / -1Question 17 of 84

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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:

$\ce{M(s) | M+(aq; 0.05 molar) || M+(aq; 1 molar) | M(s)}$

For the above electrolytic cell the magnitude of the cell potential $|E_{cell}|=70$ mV.

For the above cell

E_{cell}<0;\ \Delta G>0

E_{cell}>0;\ \Delta G<0

E_{cell}<0;\ \Delta G^0>0

E_{cell}>0;\ \Delta G^0<0

Answer and worked solution

Official answer: B

Concentration cell. Both electrodes are M | M⁺, so $E^\circ_\text{cell}=0$ and $\Delta G^\circ=0$ ; (C) and (D) are ruled out.

Spontaneous direction. As written, the anode (left) is in the dilute solution and the cathode (right) in the concentrated one:
$E=\frac{0.059}1\log\frac{1}{0.05}>0,$
so $E_\text{cell}>0$ and $\Delta G=-nFE<0$ .

(B)

Topics:Nernst equation Gibbs energy and EMF

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IIT-JEE 2010 · Paper 1, Chemistry question 17