Question

$E_1,E_2,E_3$ are the emf values of the three galvanic cells respectively. (i) $\text{Zn }|{\text{ Zn}}_{\text{1M}}^{\text{2+}}||{\text{ Cu}}_{\text{0}\text{.1M}}^{\text{2+}}|\text{ Cu}$ (ii) $Zn|Z{n}_{1M}^{2+}||C{u}_{1M}^{2+}|Cu$ (iii) $Zn|Z{n}_{0.1M}^{2+}||C{u}_{1M}^{2+}|Cu$ Which one of the following is true?

• A. $E_2>E_3>E_1$
• B. $E_3>E_2>E_1$
• C. $E_1>E_2>E_3$
• D. $E_1>E_3>E_2$

Answer 1

Answer: (B)

For the given cell, $E_{cell}=E^{o}cell-\frac{0.0591}{2}\log \frac{[Z{n}^{2+}]}{[C{u}^{2+}]}$ (i) $E_1=E^{o}cell-\frac{0.0591}{2}\log \frac{1}{0.1}=E^{o}cell-\frac{0.0591}{2}$ (ii) $E_2=E^{o}cell-\frac{0.0591}{2}\log \frac{1}{1}$ $=E^{o}cell-\frac{0.0591}{2}\times 0=E^{o}cell$ (iii) $E_3=E^{o}cell-\frac{0.0591}{2}\log \frac{0.1}{1}$ $=E^{o}cell+\frac{0.0591}{2}$ $\therefore$ $E_3>E_2>E_1$