Explore the question in detail with explanation, related questions, and community discussions.
Orthophosphoric acid (H₃PO₄), also called phosphoric acid, is a triprotic acid, meaning it has three ionizable hydrogen atoms in its molecule. The basicity of an acid refers to the number of hydrogen ions (protons) it can donate per molecule in aqueous solution.
In H₃PO₄, the three hydrogen atoms are attached to oxygen atoms, forming three –OH groups linked to the central phosphorus atom. These hydrogens are acidic and can be ionized stepwise:
H₃PO₄ → H⁺ + H₂PO₄⁻
H₂PO₄⁻ → H⁺ + HPO₄²⁻
HPO₄²⁻ → H⁺ + PO₄³⁻
Since all three protons are capable of being donated, the basicity of orthophosphoric acid is 3. This property is important in titrations, buffer preparation, and understanding phosphate chemistry.
Orthophosphoric acid is widely used in fertilizers, soft drinks, detergents, and pharmaceuticals due to its triprotic nature. The sequential loss of hydrogen ions also illustrates acid strength variation, with the first proton being the most acidic and the third the least.
Other options are incorrect:
Basicity 2 would imply only two ionizable protons.
Basicity 4 or 5 exceeds the number of acidic hydrogens in H₃PO₄.
Understanding the basicity of phosphoric acid helps students link molecular structure, ionization steps, and chemical reactivity. It is a foundational concept in inorganic chemistry, particularly when studying oxyanions, acids, and phosphate salts.
Discussion
Leave a Comment