Metals P, Q, and R have different positions in the activity series. Metal P reacts vigorously with water, metal Q reacts slowly w…

Question

Metals P, Q, and R have different positions in the activity series. Metal P reacts vigorously with water, metal Q reacts slowly with acids, and metal R does not react with water or acids. Their oxides are PO₂, QO, and R₂O₃, respectively. Considering their reactivity and the methods typically used for extraction, which of the following correctly matches the metal with its most suitable extraction method?

1. A. P - Electrolysis of molten oxide; Q - Reduction by carbon; R - Reduction by carbon.
2. B. P - Reduction by carbon; Q - Electrolysis of molten oxide; R - Electrolysis of molten oxide.
3. C. P - Electrolysis of molten oxide; Q - Reduction by carbon; R - Native metal, no extraction needed. (Correct answer)
4. D. P - Reduction by carbon; Q - Native metal, no extraction needed; R - Electrolysis of molten oxide.

Correct Answer

Option C — P - Electrolysis of molten oxide; Q - Reduction by carbon; R - Native metal, no extraction needed.

Detailed Solution & Explanation

The correct answer is P - Electrolysis of molten oxide; Q - Reduction by carbon; R - Native metal, no extraction needed.

Key Points

• The reactivity of each metal must first be placed:
  • Metal P reacts vigorously with water → it is a highly reactive metal, near the top of the activity series (like sodium, calcium or magnesium).
  • Metal Q reacts slowly with acids → it is of moderate reactivity (like zinc, iron or lead).
  • Metal R does not react with water or acids → it is a low-reactivity metal, below hydrogen (like copper, silver or gold).
• The extraction method follows directly from reactivity:
  • Highly reactive metals (P) hold their oxides so strongly that carbon cannot reduce them; they are obtained by electrolysis of the molten ore.
  • Moderately reactive metals (Q) are extracted by reduction with carbon after roasting or calcination.
  • Least reactive metals (R) occur native — in free elemental form — and need no chemical reduction at all.

Additional Information

• The three extraction zones of the activity series:

• Key processes:
  • Roasting — heating a sulphide ore in excess air to convert it to the oxide.
  • Calcination — heating a carbonate ore in limited air to convert it to the oxide.
  • Thermite reaction — $Fe_2O_3 + 2Al \rightarrow 2Fe + Al_2O_3$, an exothermic reduction used to weld railway tracks.
• Note on the oxide formulae given: PO₂, QO and R₂O₃ indicate valencies of 4, 2 and 3 respectively; these do not change the extraction logic, which depends on reactivity alone.