Physical Chemistry

Units of electrochemical conductance quantities:

• Cell constant ($G^* = l/A$): Unit is $\text{cm}^{-1}$ $\rightarrow$ (I)
• Molar conductance ($\Lambda_m = \frac{\kappa \times 1000}{M}$): Unit is $\text{ohm}^{-1}\text{ cm}^2\text{ mol}^{-1}$ $\rightarrow$ (II)
• Specific conductance ($\kappa = G \times G^*$): Unit is $\text{ohm}^{-1}\text{ cm}^{-1}$ $\rightarrow$ (III)
• Conductance ($G = 1/R$): Unit is $\text{ohm}^{-1}$ (or Siemens, S) $\rightarrow$ (IV)
  Correct match: (A)-(I), (B)-(II), (C)-(III), (D)-(IV).

Evaluating the statements for Mercury cell:

• Statement A is false: Fuel cells convert combustion energy into electrical energy, not mercury cells.
• Statement B is false: Mercury cell is a primary cell and cannot be recharged.
• Statement C is true: The overall cell reaction is $\text{Zn(Hg)} + \text{HgO}(s) \rightarrow \text{ZnO}(s) + \text{Hg}(l)$, maintaining a constant potential of $\approx 1.35\text{ V}$.
• Statement D is true: It provides a steady low current and is used in hearing aids and watches.

The lead storage battery (lead-acid accumulator) is the most widely used secondary cell. It can deliver large surge currents and is rechargeable, making it ideal for automobiles and inverters.