The acid most commonly found in swimming pools is muriatic acid, also known as hydrochloric acid. This is a very strong acid used to lower the alkalinity or pH in pools. Which of the following is the correct chemical to use in your pool?

A. HCIO₄
Incorrect. This acid has oxygen in it. The root polyatomic ion is perchlorate, which ends in –ate making it an acid that will end in –ic; this acid is perchloric acid.

B. HCl
Correct!

C. HClO
Incorrect. This is an oxyacid with a polyatomic ion base that ends in –ite, which would be changed to a –ous ending. This acid is hypochlorous acid.

D. HClO₂
Incorrect. This is an oxyacid with a polyatomic ion base that ends in –ite, which would be changed to a –ous ending. This acid is chlorous acid.

One acid you are likely to encounter in a chemistry lab is sulfuric acid. This acid reacts vigorously with water. When you mix concentrated sulfuric acid with water, it's important to add the acid to the water to minimize the chances of the reaction splashing the acid. The formula for sulfuric acid is —

A. HSO₃
Incorrect. The root polyatomic ion is bisulfite, SO₃^-1, so this acid is bisulfurous acid. (This compound is non-typical and not a polyatomic ion you will have to identify.)

B. H₂SO₃
Incorrect. The root polyatomic ion is sulfite, SO₃^-2, which, because of its –ite ending, would be changed to –ous acid. This compound is sulfurous acid.

C. H₂SO₄
Correct!

What is the name of HNO₃?

A. Nitric acid
Correct!

B. Nitrous acid
Incorrect. The –ous ending would indicate that the root polyatomic having the –ite ending which would have been NO₂.

C. Hydronitric acid
Incorrect. The hydro- prefix with the –ic acid would be indicative of a non-oxyacid.

D. Pernitric acid
Incorrect. This would not have the root polyatomic of nitrate.

What is the name of HI?

A. Lodic acid
Incorrect. There is not an oxygen indicative of the –ic acid ending.

B. Hydroiodic acid
Correct!

C. Iodious acid
Incorrect. There is no oxygen that would result in an –ous acid ending.

D. Iodine acid
Incorrect. This is not how you properly name acids.