Question

Which of the following represents the acidic component of a phosphate buffer system:

• A. Dihydrogen phosphate ion
• B. Disodium phosphate ion
• C. Sodium hydrogen phosphate ion
• D. Sodium dihydrogen phosphate ion

Hint:

Acid has more Hydrogen: $H_{2}PO_{4}^{-}$ (Acid) vs $HPO_{4}^{2-}$ (Base).

Answer 1

The Correct Option is A

Step 1: Concept
A buffer system consists of a weak acid and its conjugate base.

Step 2: Meaning
In the phosphate system, the equilibrium is between $H_{2}PO_{4}^{-}$ and $HPO_{4}^{2-}$.

Step 3: Analysis
$H_{2}PO_{4}^{-}$ (Dihydrogen phosphate) acts as the proton donor (acid), while $HPO_{4}^{2-}$ (Monohydrogen phosphate) acts as the proton acceptor (base).

Step 4: Conclusion
The dihydrogen phosphate ion is the acidic component. Final Answer: (A)