What is the name of the acid with the chemical formula HI? Select the correct answer below: Hydroiodic acid Iodic acid Hydroic acid Iodous acid
The correct answer and explanation is:
Correct Answer: Hydroiodic acid
Explanation:
The acid with the chemical formula HI is named hydroiodic acid. This name follows a standard naming convention used for binary acids, which are acids composed of hydrogen and one other nonmetal element (in this case, iodine).
Naming Binary Acids:
Binary acids typically include:
- The prefix “hydro-”
- The root of the nonmetal’s name (here, “iod” for iodine)
- The suffix “-ic”
- Followed by the word “acid”
So, HI becomes hydroiodic acid.
Why the Other Options Are Incorrect:
- Iodic acid refers to HIO₃, which contains iodine and oxygen — an oxyacid, not a binary acid.
- Hydroic acid is not a valid name; it’s a made-up term and does not follow naming rules.
- Iodous acid refers to HIO₂, another oxyacid with iodine and oxygen, and again not applicable to HI.
Chemical Properties:
Hydroiodic acid is a strong acid, meaning it completely dissociates in water into hydrogen ions (H⁺) and iodide ions (I⁻). It is one of the strongest known hydrohalic acids (acids formed from hydrogen and halogen elements), even stronger than hydrochloric (HCl) and hydrobromic (HBr) acids.
Summary:
- Formula: HI
- Name: Hydroiodic acid
- Type: Binary acid
- Strength: Strong acid (completely ionizes in water)
- Use: Commonly used in organic synthesis and as a reducing agent.
By understanding these naming conventions and chemical properties, students can correctly identify acids and their formulas in chemistry.