Question

Which of the following phosphate species does not exist in water?

• A. H₂PO₄⁻
• B. HPO₄²⁻
• C. PO₄³⁻
• D. HPO₃³⁻

Hint:

Phosphate species in water are determined by pH and include H2PO− 4 , HPO2− 4 , and PO3− 4 . HPO3− 4 is not chemically viable.

Answer 1

The Correct Option is D

The following phosphate species exist in water depending on the pH:

• H₂PO₄⁻: Exists in acidic conditions.
• HPO₄²⁻: Exists in neutral to slightly alkaline conditions.
• PO₄³⁻: Exists in highly alkaline conditions.

The species HPO₃⁴⁻ does not exist because it would require an impossible intermediate oxidation state of phosphorus.