## Chemistry: Principles and Practice (3rd Edition)

(a) HCN - hydrochloric acid (b) HNO$_3$ - nitric acid (c) H$_3$PO$_4$ - phosphoric acid
(a) HCN - hydrochloric acid Hydrogen (H), in an acid, has a valence of 1+. Cyanide (CN$^-$) has a valence of 1-. In this compound, we would need one hydrogen ion for every cyanide ion. If the name of the anion ends in $-ide$, then we add the prefix $hydro-$ to the anion, change the anion ending from $-ide$ to $-ic$, and add the word $acid$ to the end. (b) HNO$_3$ - nitric acid Hydrogen (H), in an acid, has a valence of 1+. Nitrate (NO$_3$$^-) has a valence of 1-. In this compound, we would need one hydrogen ion for every nitrate ion. If the oxoanion ends in -ate, then we drop this ending, substitute the ending -ic in its place, and add the word acid to the end. (c) H_3PO_4 - phosphoric acid Hydrogen (H), in an acid, has a valence of 1+. Phosphate (PO_4$$^{3-}$) has a valence of 3-. In this compound, we would need three hydrogen ions for every phosphate ion. If the oxoanion ends in $-ate$, then we drop this ending, substitute the ending $-ic$ in its place, and add the word $acid$ to the end.