Final answer:
Phosphoric acid (H3PO4) is a weak acid compared to perchloric acid (HClO4), chloric acid (HClO3), sulfuric acid (H2SO4), and nitric acid (HNO3), which are strong acids.
Step-by-step explanation:
The question asks about the identification of a weak acid from a list of options. Among the choices given, perchloric acid (HClO4), chloric acid (HClO3), sulfuric acid (H2SO4), and nitric acid (HNO3) are all strong acids. However, phosphoric acid (H3PO4) is not as strong as these other acids and is considered a moderately strong, or weak, acid compared to the others. This means in aqueous solution, it does not dissociate completely into ions like the strong acids do.