Question

Which refining method is used when the metal and the impurities have a low and high melting point, respectively is:

• A. Vapour phase refining
• B. Distillation
• C. Liquation
• D. Zone refining

Answer 1

The correct option is C

Liquation

The explanation for the correct option:

C: Liquation,

• Liquation is the process of refining a metal with a low melting point containing impurities of a high melting point.
• Metals with a low melting point are cleaned with this method.
• The melting point of the impurities is higher than that of the metal.
• Metals are converted to a liquid state at a temperature just above their melting point by the application of heat.
• The pure metal melts and flows out of the furnace, leaving behind the impurities.

The explanation for the incorrect options:

A: Vapour phase refining,

• Vapour phase refining is based on the principle that the impure metal is converted into a volatile compound which can be collected elsewhere.

B: Distillation,

• Distillation refers to the selective boiling and then the condensation of a component into a liquid mixture.

D: Zone refining,

• Zone refining is a very useful method for obtaining very high purity metals such as silicon and germanium.
• It is also called zone melting, floating zone process and moving zone melting.

Final answer: the correct answer is option (c) Liquation.