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Acid Nomenclature

The following describes acid formulas and names.

Remember that the names of Arrhenius acids usually end in acid (hydrochloric acid, sulfuric acid, nitric acid ) and that their formulas fit one of two general patterns.

General Formulas

HX(aq) X = F, Cl, Br, or I


For example, HCl(aq) or H2SO4

Names and Formulas for Binary Acids

Binary acids are named by writing hydro followed by the root of the name of the nometallic atom, then -ic, and finally acid: hydro(root)ic acid

The only exception to remember is that the “o” in hydro is left off for HI(aq), so its name is hydriodic acid (an acid used to make pharmaceuticals).

Most chemists refer to pure HCl gas as hydrogen chloride, but when HCl gas is dissolved in water, HCl(aq), the solution is called hydrochloric acid. We will follow the same rule in this text, calling HCl or HCl(g) hydrogen chloride and calling HCl(aq) hydrochloric acid. The same pattern holds for the other binary acids.

You will be expected to be able to write formulas and names for the binary acids found below . Remember that it is a good habit to write (aq) after the formula.

HF(aq) - hydrofluoric acid

HCl(aq) - hydrochloric acid

HBr(aq) - hydrobromic acid

HI(aq) - hydriodic acid

H2S(aq) - hydrosulfurric acid

HF - hydrogen fluoride or hydrogen monofluoride

HCl - hydrogen chloride or hydrogen monochloride

HBr - hydrogen bromide or hydrogen monobromide

HI - hydrogen iodide or hydrogen moniodide

H2S - hydrogen sulfide or dihydrogen monosulfide


Names and Formulas for Oxyacids

To name oxyacids, you must first be able to recognize them by the general formula HaXbOc, with X representing an element other than hydrogen or oxygen.

It will also be useful for you to know the names of the polyatomic oxyanions, because many oxyacid names are derived from them. If enough H+ ions are added to a (root)ate polyatomic ion to completely neutralize its charge, the (root)ic acid is formed. See below.

If one H+ ion is added to nitrate, NO3, nitric acid, HNO3, is formed.

If two H+ ions are added to sulfate, SO42−, sulfuric acid, H2SO4, is formed.

If three H+ ions are added to phosphate, PO43−, phosphoric acid, H3PO3, is formed.

Notice that the whole name for sulfur, not just the root, sulf‑, is found in the name sulfuric acid. Similarly, although the usual root for phosphorus is phosph-, the root phosphor‑ is used for phosphorus-containing oxyacids, as in the name phosphoric acid.

NO3 is nitrate, and HNO3 is nitric acid.

C2H3O2 is acetate, and HC2H3O2 is acetic acid.

SO42− is sulfate, and H2SO4 is sulfuric acid.

CO32− is carbonate, and H2CO3 is carbonic acid.

PO43− is phosphate, and H3PO4 is phosphoric acid.