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In the electrolytic refining of copper, the impurities that settle down at the bottom of the anode are known as:
Anode mud
Cathode sludge
Gangue
Flux
Anode mud
In electrolytic refining of copper, the impure copper block serves as the anode. As current passes through the electrolyte (acidified copper sulfate solution), the impurities that are less reactive than copper, such as gold, silver, and platinum, do not dissolve in the electrolyte and settle at the bottom of the anode, which is known as anode mud.
In electrolytic refining of copper, the impure copper block serves as the anode. As current passes through the electrolyte (acidified copper sulfate solution), the impurities that are less reactive than copper, such as gold, silver, and platinum, do not dissolve in the electrolyte and settle at the bottom of the anode, which is known as anode mud.
Think of it like a tea strainer; the dissolved liquid (copper ions) passes through to the cup (cathode), while the solid, insoluble tea leaves remain behind as residue (anode mud).
Cu(s)тАЛтЖТCu(aq)2+тАЛ+2eтИТ тАФ Oxidation reaction at the anode
Cu(aq)2+тАЛ+2eтИТтЖТCu(s)тАЛ тАФ Reduction reaction at the cathode
The principle involves electrolytic oxidation and reduction. At the anode, copper atoms undergo oxidation: CuтЖТCu2++2eтИТ. Noble impurities that are less electropositive than copper do not dissolve and drop down as sludge. At the cathode, pure copper ions undergo reduction: Cu2++2eтИТтЖТCu.
The anode is made of impure copper.
The cathode is made of a thin strip of pure copper.
The electrolyte is aqueous copper sulfate acidified with sulfuric acid.
The anode mud often contains valuable precious metals like gold and silver.
Yields high-purity copper (up to 99.99%)
Recovers valuable precious metal impurities
High energy consumption required for the electrolytic process
Production of high-grade copper for electrical wiring
Recovery of precious metals like Ag, Au, and Pt from industrial waste
The electrolyte used is a solution of CuSO4тАЛ and dilute H2тАЛSO4тАЛ.
Option B (Cathode sludge) is incorrect because impurities do not collect at the cathode; only pure copper deposits there.
Option C (Gangue) refers to earthy impurities like sand and rocks removed during ore concentration, not refining.
Option D (Flux) is a substance added during smelting to remove gangue by forming slag.
A is correct тАФ The insoluble impurities left behind at the anode during electrolytic refining are collectively referred to as anode mud.
Remember that anode mud only contains metals less reactive than the metal being refined; metals more reactive than copper (like Fe or Zn) dissolve into the electrolyte and do not form mud.