Chapter 5

Discuss electrochemical cell in detail with the help of a suitable example.

Define the following terms: (a) Oxidation (b) Standard electrod potential (c) Overpotential (d) Redox couple

What do you mean by electrochemical series? Discuss its important applications.

Write short notes on (a) Redox stability field of water (b) Hydrogen overpotential (c) Nernst equation(d) Disproportionation

Give reasons for (a) Sodium reacts with water to liberate hydrogen while aluminium remains safe with water. (b) \(\mathrm{Co}^{3+}\) oxidises water (c) Organic-matter rich water-logged soil contains \(\mathrm{Fe}^{2+}\) ions while oxygen-rich water contains Fe ions

Draw a Frost diagram for mercury in acid solution and comment on the tendency of the involved species to undergo disproportionation. Given \(E_{\mathrm{Hg}^{2+} / \mathrm{Hg}_{2}^{2+}}=0.911 \mathrm{~V}\) and \(E_{\mathrm{H}_{2}^{2+} / \mathrm{Hg}}^{\circ}=0.796 \mathrm{~V}\)

Determine the reduction potential \(E_{\mathrm{Sn}^{4+} / \mathrm{sn}}^{\circ}\) if \(E_{\mathrm{Sn}^{2+} / \mathrm{Sn}}^{\circ}=-0.136 \mathrm{~V}\) and \(E_{\mathrm{Sn}^{4+} / \mathrm{sn}^{2+}}^{\circ}=0.15 \mathrm{~V}\). Also draw the corresponding Latimer diagram.

Discuss the Pourbaix diagram for iron in detail.

Calculate the equilibrium constant for the possible reaction between \(\mathrm{Fe}^{2+}(\mathrm{aq})\) ions and \(\mathrm{Ce}^{4+}(\mathrm{aq})\) ions \(\mathrm{f} E_{\mathrm{Ce}^{4+} / \mathrm{ce}^{3+}}=1.44 \mathrm{~V}\) and \(E_{\mathrm{Fe}^{\circ} / \mathrm{Fe}^{2+}}^{\circ}=0.68 \mathrm{~V}\). Also comment on the spontaneity of the reaction.