Electrical resistivity is the inverse of conductivity. Silver (Ag) is the best conductor, meaning it has the lowest resistivity. Mercury (Hg) is a poor conductor compared to solid transition metals like Nickel (Ni) and Tungsten (W). Therefore, the order of increasing resistivity is Ag < W < Ni < Hg, making Hg the highest.

Electrical conductivity in electrolyte solutions occurs because the electrolyte dissociates into positively and negatively charged ions when dissolved in a solvent. Under the influence of an applied electric field, these ions migrate toward the oppositely charged electrodes. This directional movement of charged species constitutes the electric current flowing through the solution, whereas neutral molecules or solvent particles do not contribute to charge transport.

Platinising the electrodes increases their effective surface area significantly. This increase in surface area reduces the current density at the electrode-solution interface, which effectively minimizes the polarization effect (the buildup of ions at the electrode surface), ensuring more accurate conductance measurements.

Statement A is false because many liquids, such as pure water or organic solvents, are insulators. Statement R is true in the context of gas discharge physics, though the phrasing regarding liquids is unconventional. The assertion is factually incorrect as a general rule for all liquids.

The Apollo spacecraft utilized hydrogen-oxygen fuel cells to generate electricity. These cells operate by electrochemically combining hydrogen and oxygen to produce water, electricity, and heat. This technology was chosen for its high energy density and the added benefit of providing potable water for the crew during long-duration space missions.

Sulphuric acid (H2SO4) is the standard electrolyte used in lead-acid batteries, such as those found in automobiles. It facilitates the flow of ions between the lead and lead dioxide plates, enabling the chemical reactions necessary for energy storage and discharge.

Fuel cells, particularly hydrogen fuel cells, generate electricity through an electrochemical reaction between fuel and an oxidant. The only byproduct of this reaction is water vapor. Consequently, fuel cell vehicles are considered zero-emission vehicles, which significantly reduces local air pollution compared to internal combustion engines that emit CO2, NOx, and particulate matter.

During the discharge of a lead-acid battery, both the lead anode and the lead dioxide cathode are converted into lead(II) sulfate (PbSO4). While sulfuric acid is indeed consumed in the reaction, the formation of lead sulfate is the primary chemical change occurring at both electrode surfaces as the battery loses its stored electrical potential.

Dry cells (Leclanché cells) generally possess higher internal resistance compared to many other types of electrolytic or galvanic cells due to the nature of the paste electrolyte and the porous separator used, which limits ion mobility.

Statement 1 is correct as the reaction produces water and heat. Statement 2 is incorrect because fuel cells can be miniaturized for portable electronics. Statement 3 is incorrect because fuel cells produce Direct Current (DC), not AC.