JEE Main 2021 · 27 August · morning · Single correct · +4 / −1
Which refining process is generally used in the purification of low melting metals?
- (a) Chromatographic method
- (b) Liquation
- (c) Electrolysis
- (d) Zone refining
Answer and solution
Answer (b) Liquation
Solution
Chemistry ma’am · 3 steps
Low melting point is the clue: warm the impure metal gently on a slope and let it melt and flow away.
- How liquation works. The impure metal is placed on the sloping hearth of a furnace and heated to just above its melting point. The metal melts and flows down the slope. The impurities have higher melting points, so they stay behind as solid.
- Why low melting. This only works when the metal melts much more easily than its impurities. That is why liquation is used for low melting metals such as tin (Sn), lead (Pb) and bismuth (Bi).
Method Property it uses Typical use Chromatography Different adsorption of metal and impurities Small amounts, or elements present in traces Liquation Metal melts at a lower temperature than the impurities Low melting metals: Sn, Pb, Bi Electrolysis Metal dissolves at the anode and deposits at the cathode Cu, Zn, Al and many others Zone refining Impurities stay in the molten zone Ultra-pure Si, Ge, Ga for semiconductors - So. The refining method meant for low melting metals is liquation, option (b).
The idea to keep. Match each refining method to the property it uses. Low melting point means liquation, extreme purity means zone refining, and a volatile metal means distillation.
Answer from the NTA final answer key. Solution by PrepWiser.