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

• A. HClO3
• B. HCl
• C. HClO
• D. HClO2

Answer: (D)

Verified step by step guidance

1. Understand that chlorous acid is an oxyacid of chlorine, where chlorine is bonded to oxygen and hydrogen.
2. Recall the naming convention for chlorine oxyacids: 'hypochlorous acid' corresponds to HClO, 'chlorous acid' corresponds to HClO2, 'chloric acid' corresponds to HClO3, and 'perchloric acid' corresponds to HClO4.
3. Identify that the suffix '-ous' in chlorous acid indicates one oxygen less than the '-ic' acid (chloric acid, HClO3), so chlorous acid must have two oxygens.
4. Match the formula with the correct number of oxygens and hydrogens: chlorous acid is HClO2.
5. Confirm that the other options do not fit the naming pattern: HCl is hydrogen chloride (not an oxyacid), HClO3 is chloric acid, and HClO is hypochlorous acid.