Question

?Sulphan? is

• A. a mixture of $SO_3$ and $H_2SO_5$
• B. 100% conc. $H_2SO_4$
• C. a mixture of gypsum and conc. $H_2SO_4$
• D. 100% oleum (a mixture of 100% $SO_3$ in 100% $H_2SO_4$)

Answer 1

Answer: (D)

100% oleum (a mixture of 100% $SO_3$ in 100% $H_2SO_4$)

Answer 2

$H _{2} SO _{4}$ saturated with $SO _{3}$ is called oleum or sulphan.
$H _{2} SO _{4}+ SO _{3} \longrightarrow H _{2} S _{2} O _{7}$