Electrochemistry - Physical Chemistry - Chemistry Previous Year Questions

An aqueous solution contains 1.0 M of $\mathrm{X}^{2+}$ and 0.001 M of $\mathrm{Y}^2+$ ions at $25^{\circ} \mathrm{C} . \mathrm{X}^{2+}$ and $\mathrm{Y}^{2+}$ ions do not interact with each other. This solution is put in an electrolytic cell and the voltage is gradually increased till a current begins to flow through the cell. The voltage is maintained at this point and a deposit is observed on the cathode. What is the composition of the material deposited on the cathode?

(Given: Atomic weight of $X$ is 63 and $Y$ is 200.)

$$\begin{aligned} & X^{2+}+2 e^{-} \rightarrow X, E^0=0.35 \\ & Y^{2+}+2 e^{-} \rightarrow Y, E^0=0.40 \mathrm{~V} \end{aligned}$$

( $E^0$ is the standard reduction potential.)

Consider the following data for KCl solution at a particular temperature. What is the value of the limiting molar conductivity?

$$\begin{array}{|c|c|} \hline \text { Concentration }\left(\mathrm{mol} \mathrm{~L}^{-1}\right) & \text { Molar Conductivity }\left(\mathrm{S} \mathrm{~cm}^2 \mathrm{~mol}^{-1}\right) \\ \hline 1 \times 10^{-4} & 149.1 \\ \hline 9 \times 10^{-4} & 147.1 \\ \hline \end{array}$$

During the charging and discharging of a lead-acid battery (a Pb anode, a grid of Pb packed with $\mathrm{PbO}_2$ as cathode, and an aqueous solution of $\mathrm{H}_2 \mathrm{SO}_4$ as an electrolyte), which of the following redox reactions does NOT occur?

What is the value of $E^{\circ}\left(\mathrm{Fe}^{3+} / \mathrm{Fe}^0\right)$ ?

[The standard reduction potential values are $E^{\circ}\left(\mathrm{Fe}^{3+} / \mathrm{Fe}^{2+}\right)=0.77 \mathrm{~V}$, and $\left.E^{\circ}\left(\mathrm{Fe}^{2+} / \mathrm{Fe}^0\right)=-0.44 \mathrm{~V}\right]$