Electrochemistry - Physical Chemistry - Chemistry Previous Year Questions

Consider a Galvanic cell in which the following reactions occurs: $\mathrm{Fe}^{2+}(\mathrm{aq})+\mathrm{Ag}^{+}(\mathrm{aq}) \rightarrow \mathrm{Fe}^{3+}(\mathrm{aq})+\mathrm{Ag}(\mathrm{s})$. What is the standard potential of the cell? Given: $\mathrm{E}^0\left(\mathrm{Ag}^{+} / \mathrm{Ag}\right)=\mathrm{aV} \quad \mathrm{E}^0\left(\mathrm{Fe}^{2+} / \mathrm{Fe}\right)=\mathrm{bV} \quad \& \quad \mathrm{E}^0\left(\mathrm{Fe}^{3+} / \mathrm{Fe}\right)=\mathrm{cV}$

What will be the change in the electrode potential of chromium electrode dipping into chromic sulphate solution, when the electrolyte is diluted 10 times at $25^{\circ} \mathrm{C}$ ? $\left[\mathrm{E}^0\left(\mathrm{Cr}^{3+} / \mathrm{Cr}\right)\right]=-0.74 \mathrm{~V}$

Identify the correct mathematical expression which represents the variation in molar conductivity of a weak acid having concentration C and ionisation constant $\mathrm{K}_{\mathrm{a}}$

( $\lambda_m^{\infty}=$ molar conductivity at infinite dilution, $\lambda_{\mathrm{m}}=$ molar conductivity at concentration C )

Two statements, one Assertion and the other Reason are given. Choose the right option.

Assertion: The Molar conductivity of KCl increases very slowly with dilution and approaches a limiting value when dilution is infinite.

Reason: In case of KCl there is an increase in the number of ions on dilution due to complete ionisation at infinite dilution.

$3.482 \times 10^{-1} \mathrm{~g}$ of Fe gets deposited when an aqueous solution of Ferric sulphate is electrolysed for 20 minutes using a current of " $x$ " amperes. Find " $x$ ". (Atomic mass of $\mathrm{Fe}=56 \mathrm{amu}$ ).

$$\begin{aligned} &\text { Using the data given below, the strongest reducing agent is: }\\ &\begin{array}{ll} \mathrm{E}_{\mathrm{Cr}_2 \mathrm{O}_7}^{\mathrm{o}}{ }^{2-} / \mathrm{Cr}^{3+}=1.33 \mathrm{~V} & \mathrm{E}_{\mathrm{MnO}_4^{-} / \mathrm{Mn}^{2+}}^{\mathrm{o}}=1.51 \mathrm{~V} \\ \mathrm{E}_{\mathrm{Cl}_2 / \mathrm{Cl}^{-}}^{\mathrm{O}}=1.36 \mathrm{~V} & \mathrm{E}_{\mathrm{Cr}^{3+} / \mathrm{Cr}}^{\mathrm{O}}=-0.74 \mathrm{~V} \end{array} \end{aligned}$$

Which of the following is always true about a spontaneous cell reaction in a galvanic cell?

Resistance of 0.2 M solution of an electrolyte is $50 \Omega$. The conductivity of the solution is $1.3 \mathrm{Sm}^{-1}$. If the resistance of 0.4 M solution of the same electrolyte is $260 \Omega$, its molar conductivity is:

The quantity of Ca that can be produced from molten $\mathrm{CaCl}_2$, with the same quantity of electricity (in coulombs) required to produce 4.8 g of Mg from molten $\mathrm{MgCl}_2$ is: [Atomic mass of $\mathrm{Mg}=24 \mathrm{u}$; Atomic mass of $\mathrm{Ca}=40 \mathrm{u}$ ]

The $\Delta \mathrm{G}^{\circ}$ for the reaction, $C d^{2+}(a q)+Z n(s) \rightarrow Z n^{2+}(a q)+C d(s)$ is: