Arrange the following coal ranks in increasing order of atomic O/C (oxygen/carbon) ratios:
Options: (A) Peat (B) Lignite (C) Sub-bituminous (D) Low volatile bituminous (E) Anthracite
Choose the correct answer:

Correct option is C

The coal ranks can be arranged in terms of the O/C (oxygen/carbon) ratio in the following order, from the lowest to the highest O/C ratio:

1. Anthracite (E): Anthracite has the lowest O/C ratio as it is the highest rank of coal, formed under the most intense heat and pressure. The carbon content is very high and the oxygen content is very low.
2. Low volatile bituminous (D): This coal rank is also high in carbon, but with a slightly higher O/C ratio than anthracite due to its relatively lower maturity.
3. Sub-bituminous (C): This coal has more oxygen compared to bituminous coal but less than lignite, placing it in the middle of the ranks.
4. Lignite (B): Lignite has a higher O/C ratio than sub-bituminous coal as it has a lower carbon content, retaining more oxygen in its structure.
5. Peat (A): Peat has the highest O/C ratio because it is the least mature form of coal, containing the highest proportion of oxygen and the lowest proportion of carbon. It is not yet fully transformed into coal.

Information Booster:

• Coal Maturity: As coal matures from peat to anthracite, its carbon content increases, and the oxygen content decreases. This results in a decrease in the O/C ratio as coal becomes more carbon-rich and energy-dense.
• Rank of Coal: The rank of coal is determined by its degree of metamorphism. The higher the rank (from peat to anthracite), the lower the oxygen content relative to carbon.
• Oxygen/Carbon Ratio and Energy Content: As the O/C ratio decreases with increasing coal rank, the energy content of coal increases. This is why anthracite, which has the lowest O/C ratio, is the highest in energy content and is used for high-energy applications such as heating and industrial processes.

Additional Knowledge:

• Coal Ranks:
• Peat: The least mature form of coal, rich in oxygen and moisture, with the highest O/C ratio.
• Lignite: Also known as brown coal, it is a bit more carbonized than peat but still has a high O/C ratio.
• Sub-bituminous: More mature than lignite, with lower moisture and oxygen content.
• Bituminous: Further carbonized and more energy-dense, with lower O/C ratios.
• Anthracite: The most mature form of coal with the highest carbon content and the lowest O/C ratio.

Thus, the correct order is E, D, C, B, A, and the correct answer is (c).