Question

Aqueous solution of hydrogen sulphide and sulphur dioxide when mixed together, yield,
(A) sulphur and water
(B) sulphur trioxide and water
(C) Hydrogen peroxide and sulphur
(D) Hydrogen and sulphurous acid

Answer 1

Hint: Hydrogen sulfide acts as a reducing agent, especially in the presence of base, which forms SH−. At high temperatures or in the presence of catalysts, sulfur dioxide reacts with hydrogen sulfide to form elemental sulfur and water.

Complete Solution :
- Sulfur dioxide or sulphur dioxide is the chemical compound with the formula $S{{O}_{2}}$ . It is a toxic gas responsible for the smell of burnt matches. It is released naturally by volcanic activity and is produced as a by-product of copper extraction and the burning of fossil fuels contaminated with sulfur compounds.
- The Claus process is the most significant gas desulfurization process, recovering elemental sulfur from gaseous hydrogen sulfide. Hydrogen sulfide produced, for example, in the hydro-desulfurization of refinery naphthas and other petroleum oils, is converted to sulfur in Claus plants.
- Sulfur dioxide is reduced by hydrogen sulfide to give elemental sulfur at 90$^{{}^\circ }C$ . The reaction is as follows:
\[2{{H}_{2}}S+S{{O}_{2}}\xrightarrow{heat}3S+2{{H}_{2}}O\]

- Hydrogen sulfide is the chemical compound with the formula ${{H}_{2}}S$ . It is a colorless chalcogen hydride gas with the characteristic foul odor of rotten eggs. It is poisonous, corrosive, and flammable.
So, the correct answer is “Option A”.

Note: The conventional Claus process described above is limited in its conversion due to the reaction equilibrium being reached. Like all exothermic reactions, greater conversion can be achieved at lower temperatures, however as mentioned the Claus reactor must be operated above the sulfur dew point ($120150~{}^\circ C$ ) to avoid liquid sulfur physically deactivating the catalyst.