What is basicity of \(H_3PO_4\)?

3

The correct answer is option 3. 3.

The basicity of an acid refers to the number of replaceable hydrogen ions (protons) that can be donated per molecule of the acid in a reaction.

Phosphoric acid (\(H_3PO_4\)) is a triprotic acid, meaning it can donate up to three protons in sequential dissociation reactions. Let's look at the dissociation reactions of phosphoric acid:

1. \(H_3PO_4\) dissociates to donate one proton:
\[ H_3PO_4 \rightarrow H^+ + H_2PO_4^- \]

2. \(H_2PO_4^-\) dissociates to donate a second proton:
\[ H_2PO_4^- \rightarrow H^+ + HPO_4^{2-} \]

3. \(HPO_4^{2-}\) dissociates to donate a third proton:
\[ HPO_4^{2-} \rightarrow H^+ + PO_4^{3-} \]

Each dissociation reaction releases one proton. Therefore, phosphoric acid (\(H_3PO_4\)) can donate three protons successively, making it a triprotic acid.

So, the basicity of \(H_3PO_4\) is 3, indicating that it can donate three protons in acid-base reactions.