In which of the following types of coal is the percentage of carbon content the highest, making it the best grade of coal for energy production?

Introduction / Context:
Coal is a fossil fuel that exists in several forms differing in appearance, carbon content, and heating value. Understanding the different ranks of coal is important in both environmental science and industrial chemistry. This question asks which type of coal contains the highest percentage of carbon, making it the best grade for energy production.

Given Data / Assumptions:

• Different forms of coal include peat, lignite, sub bituminous, bituminous, and anthracite.
• As coal matures geologically, its carbon content generally increases.
• Higher carbon content usually means higher calorific value and less volatile matter.
• We are comparing the relative ranks of the listed coal types.

Concept / Approach:
The progression of coal formation starts with peat, followed by lignite, then sub bituminous coal, bituminous coal, and finally anthracite. At each stage, pressure and temperature drive off more volatile components and increase the proportion of fixed carbon. Anthracite is the highest rank, hardest, and contains the highest percentage of carbon, often above 90 percent. Lower rank coals like peat and lignite contain more moisture and volatile matter and less carbon, resulting in lower heating value.

Step-by-Step Solution:

Verification / Alternative check:
Approximate values from reference tables show that anthracite coal can contain over 90 percent fixed carbon, bituminous coal around 70 to 85 percent, sub bituminous around 60 to 70 percent, lignite around 50 to 60 percent, and peat much less. These numbers confirm that anthracite has the highest carbon content. Additionally, anthracite burns with a short, blue flame and little smoke, reflecting its high carbon and low volatile matter content.

Why Other Options Are Wrong:

• Bituminous: Has high carbon content but less than anthracite, so it is a lower rank coal.
• Peat: A very low rank precursor to coal with high moisture and low carbon content.
• Lignite: A soft brown coal with relatively low carbon content compared to anthracite and bituminous coal.
• Sub-bituminous coal: Intermediate between lignite and bituminous, with carbon content lower than bituminous and anthracite.

Common Pitfalls:
Students sometimes confuse bituminous with anthracite because both are used widely as fuels. Another common mistake is to think that the most common type of coal used in power plants must have the highest carbon content, which is not necessarily true. Remember that anthracite is the top grade, but it is less abundant. Learning the standard order of coal ranks helps in avoiding these errors.

Final Answer:
The form of coal with the highest percentage of carbon is Anthracite.