Question

In the extraction of crystalline silicon, an excess of silica is used to avoid the formation of:

• A. carbon dioxide
• B. carborundum
• C. silicates
• D. amorphous silicon

Answer 1

Answer: (B)

carborundum

Crystalline silicon is obtained by reducing silica with coke. When an excess of silica is heated with coke in the electric furnace in the absence of air dark grey coloured silicon is obtained in its crystalline form.

$Si{O}_2+2C⟶Si+2CO\uparrow$

Excess of silicon leads to the formation of $SiC$ (carborundum) which is an undesired product in the extraction process of silicon. So, it is avoided.