Question

Extraction of metal from the ore cassiterite involves

• A. carbon reduction of an oxide ore
• B. self-reduction of a sulphide ore
• C. removal of copper impurity
• D. removal of iron impurity

Answer 1

Answer: (D)

removal of iron impurity

Answer 2

The important ore of tin is cassiterite $(SnO_2)$. Tin is extracted from cassiterite ore by carbon reduction method in a blast furnace. Limestoneis added to produce a slug with impurities, which can be separated.
$SnO_2+2C\rightarrow Sn+2CO$
The product often contains traces of iron which is removed by blowing air through the melt to oxidise to FeO which then floats to the surface.
$2Fe+O_2\rightarrow 2FeO$

• Crude tin obtained initially contains impurities like iron, copper, lead, and other metals.
• The crude tin is subjected to a process called liquation, where it is remelted on an inclined furnace.
• Liquation takes advantage of the different melting points of tinand impurities.
• The easily fusible tin melts away and flows down, while the less fusible impurities remain behind.
• The molten tin is then further purified through a process called poling.
• Poling involves stirring the molten tin with green poles of wood in the presence of air.
• During poling, any remaining metal impurities react with oxygen in the air and form scum.
• The scum rises to the surface of the molten tin and is removed, leaving behind purified tin.
• Poling helps in oxidizing and removing the remaining impurities in the molten tin.

Therefore, Options A, C, and D are the correct answers.

Discover More From Chapter:General Principles and Processes of Isolation of Elements