Question

Identify the incorrect statement.
A. Graphite is a thermodynamically more stable allotrope of carbon.
B. Other forms of elemental carbon like coke, carbon black, charcoal are impure forms of carbon.
C. All allotropes of carbon have thermodynamically the same stability.
D. Charcoal and coke are obtained by heating wood in the absence of air.

Answer 1

Hint: An allotrope: It is another form of the same element having different physical properties but the same chemical properties. They are different in physical properties but resemble carbon in chemical properties.

Complete answer:
Graphite is the most thermodynamically stable allotrope of carbon. Its standard enthalpy of formation is - zero, as it is the most stable form. Therefore, this statement is correct.
An impure form of carbon is that which contains other atoms or compounds other than carbon. Lignite which contains Carbon, Sulphur, and moisture is the impure form of carbon. Yes, other forms of elemental carbon like coke, carbon black, charcoal are impure forms of carbon.
Yes, all allotropes of carbon have thermodynamically the same stability. Although graphite is more stable thermodynamically as compared to diamond.
Coke is formed by the destructive distillation of coal. It is the process of heating coal without oxygen to get useful products. The immediate black residue gathered is coke alongside these hot fumes which produce coal gas, liquor ammonia, and coal tar on the further destructive distillation process.
Charcoal is obtained from heating wood whereas coke is obtained from heating coal.
Hence, the correct option is D.

Note: The possibility to make a mistake is that you may choose option A. But graphite has one delocalized electron per carbon. Due to this, the attraction between carbon atoms increases, so there will be strong bonding which gives more stability to the structure.