Question

Which of the following is dynamically the most stable state of carbon?

• A. Diamond
• B. Graphite
• C. Fullerene
• D. All of these

Hint:

Graphite is the thermodynamically standard state of carbon.
This is why standard enthalpies of formation for carbon compounds are calculated relative to graphite, not diamond.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks which allotrope of carbon is thermodynamically (referred to as dynamically in some translation contexts) the most stable state under standard temperature and pressure conditions.

Step 2: Key Formula or Approach:
Thermodynamic stability is determined by the standard Gibbs free energy or enthalpy of formation.
The allotrope with the lowest standard enthalpy of formation (\(\Delta H_f^\circ = 0\)) is considered the most stable state.

Step 3: Detailed Explanation:

• Carbon exists in several allotropic forms, primarily diamond, graphite, and fullerene.

• Graphite has a layered, planar structure where each carbon atom is \(sp^2\) hybridized and bonded to three other carbon atoms in a hexagonal ring pattern.

• This structure possesses a highly delocalized system of \(\pi\) electrons, which provides extra resonance stabilization.

• Thermodynamically, graphite is more stable than diamond by about \(2.9\text{ kJ/mol}\) under standard conditions of room temperature and atmospheric pressure.

• Consequently, the standard enthalpy of formation of graphite is defined as zero, and other allotropes like diamond and fullerene can theoretically convert to graphite over a very long geological timescale.


Step 4: Final Answer:
Therefore, graphite is the most stable state of carbon.