What is the Difference Between Oleum and Sulfuric Acid?

The main difference between oleum and sulfuric acid lies in their composition and properties.

Oleum:

• Also known as fuming sulfuric acid, it is a solution of sulfur trioxide (SO3) in sulfuric acid.
• The chemical formula for oleum is ySO3·H2O, where y represents the total molar content of sulfur trioxide.
• Oleum is an oily, colored, or cloudy liquid due to the presence of impurities.
• It generates strong fumes when exposed to air and is diluted with considerable heat generation when in contact with water.
• Oleum is generally less corrosive to metals than sulfuric acid because there is no free water to attack surfaces.

Sulfuric Acid:

• An inorganic acid, it is produced by the contact process from elementary sulfur.
• Sulfuric acid is an aqueous solution of sulfuric acid and has a strong acidic nature.
• It is a clear, oily, colorless to slightly clouded liquid that is well miscible with water.
• Sulfuric acid is hygroscopic and has corrosive effects, carbonizing most organic substances.
• It is widely used in various applications, such as fertilizer production, oil refining, wastewater processing, and chemical synthesis.

In summary, oleum is a solution of sulfur trioxide in sulfuric acid, while sulfuric acid is a standalone inorganic acid. Oleum has a more complex composition and is generally less corrosive than sulfuric acid.

Comparative Table: Oleum vs Sulfuric Acid

Here is a table comparing the differences between oleum and sulfuric acid:

The key difference between oleum and sulfuric acid lies in the concentration of sulfur trioxide in the compound. Oleum is a mixture of sulfuric acid with up to 80% free sulfur trioxide, while sulfuric acid itself contains sulfur trioxide in a less concentrated form.