Question

Which of the following is correct expression for the zinc amalgam electrode?

• A. $E_{Z{n}^{2+}/Zn}=E_{Z{n}^{2+}/Zn}^0-\frac{2.303RT}{2F}log\frac{\left[Zn\right(Hg\left)\right]}{\left[Z{n}^{2+}\right]}$
• B. $E_{Z{n}^{2+}/Zn}=E_{Z{n}^{2+}/Zn}^0+\frac{2.303RT}{2F}log\frac{\left[Zn\right(Hg\left)\right]}{\left[Z{n}^{2+}\right]}$
• C. $E_{Z{n}^{2+}/Zn}=E_{Z{n}^{2+}/Zn}^0+\frac{2.303RT}{2F}log\frac{1}{\left[Z{n}^{2+}\right]}$
• D. $E_{Z{n}^{2+}/Zn}=E_{Z{n}^{2+}/Zn}^0-\frac{2.303RT}{F}log\frac{1}{\left[Z{n}^{2+}\right]}$

Answer 1

The correct option is A $E_{Z{n}^{2+}/Zn}=E_{Z{n}^{2+}/Zn}^0-\frac{2.303RT}{2F}log\frac{\left[Zn\right(Hg\left)\right]}{\left[Z{n}^{2+}\right]}$

The alloy of any metal with mercury is called amalgam.
Amalgam electrode is a modification of metal–metal soluble salt electrode. In place of a metal, its solution in mercury is used.

In zinc amalgam electrode, zinc amalgam is used in the place of solid $Zn$ rod.

The half cell reduction reaction is
$Z{n}^{2+}+2e^{-}\to Zn\left(Hg\right)$

Reduction potential of the electrode is
$E_{Z{n}^{2+}/Zn}=E_{Z{n}^{2+}/Zn}^0-\frac{2.303RT}{2F}log\frac{\left[Zn\right(Hg\left)\right]}{\left[Z{n}^{2+}\right]}$