Question

Hoop's process is predominantly used for the electrolytic refining of

• A. copper
• B. tin
• C. zinc
• D. aluminium

Hint:

Associate key metallurgical processes with their specific metals: - Hall-Héroult & Hoope's Process: Aluminium - Bessemer & LD Process: Steel (Iron) - Mond Process: Nickel - Van Arkel Method: Titanium, Zirconium - Parkes Process: Silver (from lead)

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
This question asks to identify the metal for which Hoope's process (a specific method of electrolytic refining) is used. Electrolytic refining is a process used to obtain very high purity metals.

Step 2: Detailed Explanation:
Let's review the refining processes for the metals listed: -

Copper: Copper is refined electrolytically using an impure copper anode, a pure copper cathode, and an aqueous solution of copper sulfate as the electrolyte. This is a very common and important industrial process but is not called Hoope's process. -

Tin: Tin is often refined by a process called liquation or by electrolysis. -

Zinc: Zinc can be refined by distillation (due to its low boiling point) or electrolysis. -

Aluminium: The primary extraction of aluminium is done by the Hall-Héroult process. For further purification to obtain very high purity (99.99%) aluminium, Hoope's electrolytic refining process is used. Hoope's Process: This process uses a special electrolytic cell with three distinct liquid layers of different densities: -

Bottom Layer (Anode): Molten impure aluminium alloyed with copper. -

Middle Layer (Electrolyte): A molten mixture of fluorides (e.g., cryolite, BaF₂). -

Top Layer (Cathode): Molten pure aluminium. During electrolysis, aluminium ions from the middle layer are deposited at the cathode (top layer), becoming pure aluminium. Simultaneously, an equivalent amount of aluminium from the impure anode (bottom layer) dissolves into the electrolyte, replenishing the aluminium ions. Impurities are left behind in the anode layer. This three-layer process is characteristic of Hoope's process for refining aluminium.

Step 3: Final Answer:
Hoope's process is used for the electrolytic refining of aluminium. This corresponds to option (D).