Match the entries of column I with appropriate entries of column II and choose the correct option out of the four options given.
| Column I | Column II |
| (i) Lead storage battery | (a) maximum efficiency |
| (ii) Mercury cell | (b) prevented by galvanisation |
| (iii) Fuel cell | (c) gives steady potential |
| (iv) Rusting | (d) Pb is anode, PbO2 is cathode |
Answer & explanation
Correct answer: option 4
(i) Lead storage battery: The most important secondary cell is the lead storage battery commonly used in automobiles and invertors. It consists of a lead anode and a grid of lead packed with lead dioxide (PbO2) as cathode. A 38% solution of sulphuric acid is used as an electrolyte.
(ii) Mercury cell: Mercury cell is suitable for low current devices like hearing aids, watches, etc. The cell potential is approximately 1.35 V and remains constant during its life as the overall reaction does not involve any ion in solution whose concentration can change during its lifetime.
(iii) Fuel cell: The cell runs continuously as long as the reactants are supplied. Fuel cells produce electricity with an efficiency of about 70% compared to thermal plants whose efficiency is about 40%. There has been tremendous progress in the development of new electrode materials, better catalysts and electrolytes for increasing the efficiency of fuel cells.
(iv) Rusting: Rusting of iron is prevented by coating a layer of zinc on its surface. This process is termed as galvanisation.