(a) The conductivity of $0.1\text{ mol L}^{-1}$ solution of $\text{NaCl}$ is $1.06 \times 10^{-2}\text{ S cm}^{-1}$. Calculate its molar conductivity and degree of dissociation. $\lambda^\circ_{\text{Na}^+} = 50.1\text{ S cm}^2\text{ mol}^{-1}$ $\lambda^\circ_{\text{Cl}^-} = 76.5\text{ S cm}^2\text{ mol}^{-1}$ (b) (i) Following cell reaction occurs in a galvanic cell : $2\text{Ag}^+_{(\text{aq})} + \text{Zn}_{(\text{s})} \longrightarrow 2\text{Ag}_{(\text{s})} + \text{Zn}^{2+}_{(\text{aq})}\text{ E}^\circ_{(\text{cell})} = +1.56\text{ V}$ Predict the direction of flow of current. (ii) Differentiate between a primary battery and a secondary battery. OR

(a) Resistance of a conductivity cell filled with $0.1\text{ M KCl}$ solution is $100\text{ }\Omega$. If the resistance of the same cell when filled with $0.01\text{ mol L}^{-1}\text{ KCl}$ solution is $300\text{ }\Omega$, calculate the conductivity and molar conductivity of $0.01\text{ mol L}^{-1}\text{ KCl}$ solution. The conductivity of $0.1\text{ M KCl}$ solution is $1.29 \times 10^{-2}\text{ S cm}^{-1}$. (b) (i) Write any two advantages of $\text{H}_2 - \text{O}_2$ fuel cell. (ii) Why does the cell potential of mercury cell remain constant throughout the life ?