Question

Fuming sulphuric acid is commercially known as:
A. Caro's acid
B. Marshall’s acid
C. Oleum
D. Sulphurous acid

Answer 1

Hint: Oleum is commercially called fuming sulphuric acid. Oleum is formed from sulphur trioxide and concentrated sulfuric acid. This has many applications.

Complete step by step answer:
Fuming sulfuric acid, is commercially called oleum, it is formed by dissolving sulfur trioxide \[{\text{ }}\left( {{\text{S}}{{\text{O}}_{\text{3}}}} \right)\] in concentrated sulfuric acid \[\left( {{{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}} \right)\]. This forms a mixture of compounds like sulphuric acid, disulfuric acid and free sulphur trioxide. Formed Sulfur trioxide is volatile and causes the acid to fume, creating a cloud of tiny sulfuric acid droplets. Fuming sulfuric acid is produced in the industrial process to make sulfuric acid. A small proportion is retained as oleum and it is used in the manufacture of certain explosives, drugs and dyes.
The first step in the industrial process to manufacture sulfuric acid is oxidizing sulfur dioxide to give sulfur trioxide. This sulfur trioxide reacts with water to give sulfuric acid. But this reaction is too violent to be controlled, and so, the sulfur trioxide is instead dissolved in existing concentrated sulfuric acid to form oleum, the fuming sulfuric acid. Major product is converted to sulfuric acid by careful addition of it to the appropriate volume of water. When the oleum is added to the water, the reaction is exothermic, but is controllable. The oleum remains are used for industrial purposes.

So, the correct answer is Option C.

Additional Information:
Caro’s acid and Marshall’s acid are both inorganic acid compounds. They contain sulfate groups. They are named peroxymonosulfuric acid and peroxydisulfuric acid, respectively.

Note: Fuming sulfuric acid is a more powerful dehydrating agent than sulfuric acid. It reacts with water very violently, causing the release of a great deal of heat and acid spray, it can be reduced by adding slowly to the water. It behaves like sulfuric acid, it removes water from carbohydrates, leaving only carbon, so that it chart paper, wood also many organic materials. A large amount of heat is released by this reaction that it causes combustion.