Question

At equimolar concentrations of Fe2+ and Fe3+, what must [Ag+] be so that the voltage of the galvanic cell made from the (Ag+ | Ag) and (Fe3+ | Fe2+) electrodes equals zero ?$\text{F}\text{e}^{\text{2+}}\text{ + A}\text{g}^{+}\text{ F}\text{e}^{\text{3+ }}\text{+ Ag}$

${E^{0}}_{Ag^{+}|Ag} = 0.7991;{E^{0}}_{Fe3 + |Fe2 +} = 0.771$

• A. 0.34
• B. 0.44
• C. 0.47
• D. 0.61

Answer 1

Answer: (A)

0.34

Answer 2

$\text{0 = }(\text{-0.771 + 0.7991})\text{ - }\frac{\text{0.0591}}{1}\text{ log}\frac{1}{x} \Rightarrow \text{0 = 0.0281 +0.0591 log X }$

$\log X = - \frac{0.0281}{0.0591} \Rightarrow x = 0.335M$