Question

The conjugate base of \(H_2PO_4^{-}\) is:

• A. \(HPO_4^{-}\)
• B. \(PO_4^{2-}\)
• C. \(H_2PO_4^{2-}\)
• D. \(HPO_4^{2-}\)

Hint:

Conjugate base = acid − \(H^+\). Charge decreases by 1 unit of negative charge increase.

Answer 1

The Correct Option is D

Step 1: Defining conjugate base.
A conjugate base results when an acid donates one proton (H⁺).

Step 2: Starting species.
H₂PO₄⁻ carries a -1 charge with two acidic hydrogens.

Step 3: Removing a proton.
Loss of H⁺ transforms H₂PO₄⁻ into HPO₄²⁻, making the charge more negative by one unit.

Step 4: Charge balance verification.
Original charge -1 minus (+1) equals -2, consistent with HPO₄²⁻.

Step 5: Conclusion.
The conjugate base is HPO₄²⁻.