Question

The oxidation potentials of Zn, Cu, Ag, H2 and Ni are 0.76, –0.34, –0.80, 0.00, 0.25 volt, respectively. Which of the following reactions will provide maximum voltage ?

• A. $\text{Zn + C}\text{u}^{\text{2+}}\ \overset{\quad\quad}{\rightarrow}\text{Cu + Z}\text{n}^{2 +}$
• B. $\text{Zn + 2A}\text{g}^{+}\ \overset{\quad\quad}{\rightarrow}\text{2Ag + Z}\text{n}^{\text{2+}}$
• C. $H_{2}\text{ + C}\text{u}^{\text{2+}}\overset{\quad\quad}{\rightarrow}2^{\text{H+}}\text{ + Cu}$
• D. $H_{2}\text{ + N}\text{i}^{\text{2+}}\overset{\quad\quad}{\rightarrow}\text{ 2}\text{H}^{+}\text{ + Ni}$

Answer 1

Answer: (A)

$\text{Zn + C}\text{u}^{\text{2+}}\ \overset{\quad\quad}{\rightarrow}\text{Cu + Z}\text{n}^{2 +}$

Answer 2

$E_{cell} = 0.77 - \frac{0.059}{1}\log\frac{1.5}{0.015} = 0.652V$