Which one of the following is the chemical formula of Hypobromous acid ?
- A.HBrO₄
- B.HOBr
- C.HBr
- D.HBrO₃
Correct answer
Explanation
The correct answer is B, HOBr. Hypobromous acid has one hydrogen, one oxygen and one bromine atom, with bromine in the +1 oxidation state.
The oxyacids of a halogen are named by how much oxygen they hold. For bromine the series runs: hypobromous acid HOBr (+1), bromous acid HBrO₂ (+3), bromic acid HBrO₃ (+5) and perbromic acid HBrO₄ (+7). The prefix "hypo" marks the lowest oxygen content and "per" the highest. Hypobromous acid is a weak, unstable acid that forms when bromine dissolves in water, and like hypochlorous acid it acts as a bleach and disinfectant.
A is wrong: HBrO₄ is perbromic acid, with bromine at +7.
C is wrong: HBr is hydrobromic acid, which has no oxygen at all.
D is wrong: HBrO₃ is bromic acid, with bromine at +5.
Exam tip: hypo-ous (+1), -ous (+3), -ic (+5), per-ic (+7) is the naming pattern for the oxyacids of chlorine, bromine and iodine.
Practice Questions
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