Question

Which of the following trioxides can exist as monomeric molecule?

• A. $S{O}_3$ in solid state
• B. $Se{O}_3$ in all state
• C. $Te{O}_3$
• D. $S{O}_3$ in gaseous state

Answer 1

The correct option is A $S{O}_3$ in solid state

• Sulfur trioxide can exist in both monomeric and polymeric forms. In the gaseous and liquid state, pure $S{O}_3$ is an equilibrium mixture of monomeric $S{O}_3$ and trimeric $S_3{O}_9$, also called $Y-S{O}_3.$
  
• In solid state it exists as monomeric $S{O}_3$.