The key difference between oleum and sulfuric acid is that the oleum is sulfur trioxide in sulfuric acid whereas the sulfuric acid is an inorganic acid having the chemical formula H2SO4.
We call oleum as “fuming sulfuric acid” as well. It has sulfur trioxide in sulfuric acid but in various compositions. We can write the chemical formula for this syrupy liquid as ySO3.H2O in which “y” gives the total molar content of sulfur trioxide. Sulfuric acid, on the other hand, is a syrupy liquid, which is highly water soluble. It is also hygroscopic. This acid has a strong acidic nature as well. More details are below.
CONTENTS
1. Overview and Key Difference
2. What is Oleum
3. What is Sulfuric Acid
4. Side by Side Comparison – Oleum vs Sulfuric Acid in Tabular Form
5. Summary
What is Oleum?
The oleum is “fuming sulfuric acid” which has sulfur trioxide in various compositions in sulfuric acid. The chemical formula of this compound is ySO3.H2O in which “y” gives the total molar content of sulfur trioxide. When the value of y is changed, we can get a series of oleum. Another equivalent formula is H2SO4.xSO3. There the “x” gives molar free sulfur trioxide content. The production process of this compound is “contact process”. There, we first oxidize sulfur into sulfur trioxide. Then we can dissolve this product in concentrated sulfuric acid. Furthermore, if we dilute oleum, it regenerates sulfuric acid.
Figure 01: Oleum in a Bottle
During earlier times, manufacturers used lead chamber process for this production, but now it is not in use due to the corrosion of lead from sulfuric acid. There are important applications of oleum, for example, it i important as an intermediate for the production of sulfuric acid. In addition, it is important as a medium for the transportation of sulfuric acid. This compound is highly corrosive; hence, it is useful as a harsh reagent in researches. Moreover, we can use it in the manufacturing of explosives.
What is Sulfuric Acid?
Sulfuric acid is an inorganic acid having the chemical formula H2SO4. It is a colorless and odorless liquid which is highly syrupy. It readily dissolves in water. The reaction of this dissolution is highly exothermic. In addition, it is highly hygroscopic. This compound has a strong acidic nature and thus, it is highly corrosive. Therefore, the concentrated form of this acid is harmful when in contact with skin.
Figure 02: Sulfuric Acid
The molar mass of this compound is 98.07 g/mol. The most common application of this acid is to produce fertilizers. In addition, it is useful in oil refining, wastewater processing and synthesis of different chemicals.
What is the Difference Between Oleum and Sulfuric Acid?
The oleum is “fuming sulfuric acid” which has sulfur trioxide in various compositions in sulfuric acid. We can write the chemical formula of this compound as ySO3.H2O or H2SO4.xSO3. Moreover, the molar mass of this compound varies with different compositions of sulfur trioxide. Sulfuric acid is a mineral acid. The chemical formula of this compound is H2SO4. In addition, the molar mass of it is 98.07 g/mol. This is the main difference between oleum and sulfuric acid.
Summary – Oleum vs Sulfuric Acid
The oleum is an important source of sulfuric acid. The difference between oleum and sulfuric acid is that the oleum is sulfur trioxide in sulfuric acid whereas the acid is and an inorganic acid having the chemical formula H2SO4.
Reference:
1. “Oleum.” Wikipedia, Wikimedia Foundation, 19 June 2018. Available here
2. “Sulfuric Acid.” Wikipedia, Wikimedia Foundation, 25 June 2018. Available here
Image Courtesy:
1.’Oleum 100ml’By W. Oelen (CC BY-SA 3.0) via Commons Wikimedia
2.’Sulfuric Acid’By Zoefkris – Own work, (CC BY-SA 4.0) via Commons Wikimedia