Question

Which of the following is tribasic acid:

Options

• H₃PO₃

• H₃PO₂

• H₃PO₄

• H₂SO₄

Answer 1

H₃PO₄

Explanation:

A tribasic acid is one that can release three replaceable hydrogen ions (H⁺) per molecule when dissolved in water. In orthophosphoric acid (H₃PO₄), all three hydrogen atoms are bonded directly to highly electronegative oxygen atoms as –OH groups, making them easy to ionise. In contrast, H₃PO₃ is dibasic, and H₃PO₂ is monobasic because their remaining hydrogen atoms are attached directly to phosphorus and cannot be released.