Question

Zone refining is used for the purification of:

• A. Au
• B. Ge
• C. Ag
• D. Cu

Hint:

Zone refining gives ultra high purity, used mainly for semiconductors like germanium.

Answer 1

The Correct Option is B

Step 1: Recall the principle of zone refining.
Zone refining works on the principle that impurities are more soluble in the molten state of a substance than in its solid state. A moving heater melts a narrow zone of a rod, impurities concentrate in the molten zone and move along with it towards one end, leaving pure solid behind.

Step 2: Recall where this method is applied.
This method is used for materials that must be extremely pure, at the level of parts per billion, mainly semiconductors like germanium and silicon, since even tiny impurity levels change their electrical properties drastically.

So option B, Ge (germanium), is correct.

Why the others are wrong: Gold (option A) and silver (option C) are usually purified by methods like cupellation or electrolytic refining, not zone refining. Copper (option D) is refined by electrolytic refining, which is more economical for a metal needed in bulk and does not require the ultra high purity of semiconductor grade material.