Which of the following is the correct chemical formula for sulfurous acid?

• A. H2S
• B. H2SO3
• C. H2SO4
• D. HSO3

Answer: (B)

Verified step by step guidance

1. Understand that sulfurous acid is an oxyacid of sulfur, meaning it contains hydrogen, sulfur, and oxygen atoms.
2. Recall that sulfurous acid is formed when sulfur dioxide (SO2) dissolves in water, leading to the formula containing sulfur and three oxygen atoms.
3. Recognize that the general formula for sulfurous acid is H2SO3, where two hydrogen atoms balance the charge of the sulfite ion (SO3^2-).
4. Compare the given options: H2S is hydrogen sulfide (no oxygen), H2SO4 is sulfuric acid (with four oxygens), and HSO3 is not a neutral acid formula but rather a possible ion.
5. Conclude that the correct chemical formula for sulfurous acid is H2SO3, as it correctly represents the composition of the acid with two hydrogens, one sulfur, and three oxygens.