The lead-acid accumulator consists of

Analyze the question: We need to identify the correct components of a lead-acid accumulator (the type of rechargeable battery used in cars).

Concept: A lead-acid accumulator has three main parts:

• Positive electrode (anode on discharge): lead(IV) oxide, PbO₂ (brown in colour)
• Negative electrode: spongy lead, Pb
• Electrolyte: dilute sulphuric acid, H₂SO₄ (also called tetraoxosulphate(VI) acid)

Checking each option:

• A. Lead as the positive electrode: Wrong. The positive plate is lead(IV) oxide, not pure lead. Pure (spongy) lead is the negative plate.
• B. Lead acid as the negative electrode: Wrong. "Lead acid" is not an electrode material. The negative electrode is lead.
• C. Hydrochloric acid as the electrolyte: Wrong. Hydrochloric acid is not used, because the chloride would react differently and would not form the insoluble PbSO₄ that the cell's chemistry depends on.
• D. Tetraoxosulphate(VI) acid as the electrolyte: Correct. This is the IUPAC-style Nigerian name for H₂SO₄, the dilute sulphuric acid used in the accumulator.

Reaction summary (discharge): Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O

During charging, this reaction is reversed. This is why it is called an accumulator, as it can be recharged.

Exam tip: Remember "Positive = PbO₂, Negative = Pb (spongy lead), electrolyte = sulphuric acid." Also, whenever you see "tetraoxosulphate(VI) acid" in JAMB, translate it to H₂SO₄ right away.