Question

Consider the following concentration cell:

$Zn\left(s\right)|Z{n}^{2+}\left(0.024M\right)||Z{n}^{2+}\left(0.480M\right)|Zn\left(s\right)$

Which of the following statement is (are) correct?

• A. The EMF of the cell at ${25}^{\circ }C$ is nearly 0.038 V.
• B. The EMF of the cell at ${25}^{\circ }C$ is nearly -0.038 V.
• C. If water is added in LHE, so that the $\left[Z{n}^{2+}\right]$ is reduced to 0.012 M, the cell voltage increases.
• D. If water is added in LHE, so that the $\left[Z{n}^{2+}\right]$ is reduced to 0.012 M, the cell voltage remains same.

Answer 1

Answer: (A), (C)

The EMF of the cell at ${25}^{\circ }C$ is nearly 0.038 V.
If water is added in LHE, so that the $\left[Z{n}^{2+}\right]$ is reduced to 0.012 M, the cell voltage increases.

For the concentration cell, $E_{cell}^{\ominus }=0$

a. $E_{cell}=0-\frac{0.059}{2}log\frac{0.024}{0.48}=0.038V$

c. $\left[Z{n}^{2+}\right]$ new in LHE = 0.012

$\therefore E_{cell}^{\prime }=0-\frac{0.059}{2}log\frac{0.012}{0.48}=0.0472$

$\therefore E_{cell}^{\prime }>E_{cell}$

Hence, options A and C are correct