The following acids are monobasic except

A monobasic acid is an acid that can donate only one hydrogen ion (H+) or proton per molecule in an acid-base reaction. Out of the given acids, all except ethanedioic acid (also known as oxalic acid) are monobasic. Methanoic acid, also known as formic acid, has the formula HCOOH and can donate one hydrogen ion (H+) in an acid-base reaction. Dioxonitrate III acid, also known as nitrous acid, has the formula HNO2 and can donate one hydrogen ion (H+) in an acid-base reaction. Oxochlorate (I) acid, also known as hypochlorous acid, has the formula HClO and can donate one hydrogen ion (H+) in an acid-base reaction. Hydrobromic acid has the formula HBr and can donate one hydrogen ion (H+) in an acid-base reaction. Ethanedioic acid, also known as oxalic acid, has the formula H2C2O4 and can donate two hydrogen ions (H+) in an acid-base reaction, making it a dibasic acid.