Which of the following is an allotropic form of carbon used in lead pencils?
A. Graphite
B. Fullerene
C. Charcoal
D. Diamond
Answer: Option A
Solution (By JKSSB Mock Tests)
Graphite mixed with clay forms pencil 'lead'. Its layered structure marks paper. Diamond is used in cutting, fullerene in nanotechnology, charcoal in filters and fuel.
Explanation:
Gypsum (CaSO₄·2H₂O) is added to clinker to slow down the rapid setting of C₃A, providing workable time. Without gypsum, flash set occurs.
Explanation:
In electrolytic refining, impure copper is the anode, pure copper is the cathode, and CuSOâ‚„ acidified with Hâ‚‚SOâ‚„ is the electrolyte. Copper dissolves from anode and pure copper deposits on cathode. Smelting is reduction with coke.
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