Question

Sulphan is:
A. a mixture of ${\text{S}}{{\text{O}}_{\text{3}}}$ and ${{\text{H}}_2}{\text{S}}{{\text{O}}_{\text{5}}}$.
B. 100. conc. ${{\text{H}}_2}{\text{S}}{{\text{O}}_{\text{4}}}$.
C. a mixture of gypsum and conc. ${{\text{H}}_2}{\text{S}}{{\text{O}}_{\text{4}}}$.
D. 100% oleum (a mixture of 100% ${\text{S}}{{\text{O}}_{\text{3}}}$ and 100% ${{\text{H}}_2}{\text{S}}{{\text{O}}_{\text{4}}}$).

Answer 1

Hint : The other name of sulphan is oleum. The molecular formula of oleum is ${{\text{H}}_{\text{2}}}{{\text{S}}_{\text{2}}}{{\text{O}}_{\text{7}}}$. From the molecular formula of oleum, the components which are involved in the mixture can be determined easily.

Complete step by step solution :
Sulphan is also referred to as oleum. The molecular formula of oleum is ${{\text{H}}_{\text{2}}}{{\text{S}}_{\text{2}}}{{\text{O}}_{\text{7}}}$. It is made from mixture of 100% sulphuric acid $\left( {{{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}} \right)$ and 100% sulphur trioxide$\left( {{\text{S}}{{\text{O}}_{\text{3}}}} \right)$. The reaction is as follows:
${{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}} + {\text{S}}{{\text{O}}_{\text{3}}} \to {{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{7}}}\left( {{\text{oleum}}} \right)$
Thus sulphan is 100% oleum which is made from 100% ${\text{S}}{{\text{O}}_{\text{3}}}$ and 100% ${{\text{H}}_2}{\text{S}}{{\text{O}}_{\text{4}}}$. Therefore, the correct option is D.

Additional Information: Sulphan is an extensively strong dehydrating agent (removal of water) which means it has the capability to remove all the water molecules from any compound. It is a thick corrosive substance. Sulphan is prepared through a contact process. Contact process is mainly utilized for the preparation of sulphuric acid $\left( {{{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}} \right)$.
The contact process includes the conversion of sulphur dioxide gas $\left( {{\text{S}}{{\text{O}}_{\text{2}}}} \right)$ into sulphur trioxide $\left( {{\text{S}}{{\text{O}}_{\text{3}}}} \right)$ in the availability of catalyst such as platinum or vanadium pentoxide $\left( {{{\text{V}}_2}{{\text{O}}_5}} \right)$. The sulphur trioxide formed is absorbed in concentrated sulphuric acid which leads to the formation of oleum. The reaction of oleum with water produces sulphuric acid.

Note : Sulphan is also known as 100% oleum. Remember the molecular formula of oleum that is ${{\text{H}}_{\text{2}}}{{\text{S}}_{\text{2}}}{{\text{O}}_{\text{7}}}$. It is made from 100% conc. sulphuric acid saturated with 100% sulphur trioxide (excess).