Question

Oleum is also known as:
A. Castor oil
B. Oil of vitriol
C. Fuming sulfuric acid
D. None of these

Answer 1

‌ Oleum produced by the contact process in sulfur is oxidized into sulfur trioxide and sulfur trioxide is dissolved in concentrated sulfuric acid. Sulfur Trioxide could be a white gas having the looks of fog. It also features a sharp, penetrating odor that's detectable at low concentrations and sulfuric acid is a strong acid that is used as an oxidizing agent and dehydrating agent.

Complete answer:
Adding an amount of sulfur in far more than oxygen to gas within the presence of the catalyst vanadic acid at ${450^ \circ }{\text{C}}$ and 1-2 atm. The sulfur trioxide formed is added to sulfuric acid which supplies rise to oleum. The oleum is then added to water to make acid which is incredibly concentrated.
The contact process could be a present method of manufacturing concentrated acid which is required for industrial use. The catalyst used during the method is vanadium oxide.
The equation of formation of oleum is given by,
$S{O_3} + {H_2}S{O_4} \to {H_2}{S_2}{O_7}$
The number of Sulfur in oleum is 2
Oleum could be a dense, thick fuming yellow liquid. Density is 2 $\dfrac{{Kg}}{L}$. Very toxic by inhalation corrosive liquid consisting of concentrated vitriol (Fuming sulfuric acid) containing excess sulfur trioxide in solution.
In oleum $S{O_3}$ fumes evolve and combine with moisture and form sulfuric acid due to evolution of fumes oleum is also known as fuming sulfuric acid.
Castor oil is a triglyceride, which chemically is a glycerol molecule with each of its three hydroxyl groups esterified with a long-chain fatty acid. Its major fatty acid is the unsaturated, hydroxylated 12-hydroxy, 9-octadecenoic acid, known as ricinoleic acid. Hence oleum is not castor oil
Therefore the correct option is option C..

Note: The foremost use of acid is within the production of fertilizers, superphosphate of lime and ammonium sulfate. It's widely employed in the manufacture of chemicals, in making acid, aqua forts, sulfate salts, synthetic detergents, dyes and pigments, explosives, and drugs.