Question

What is the basicity of H₃PO₄?

Answer 1

H₃PO₄ has three ionisable hydrogen atoms. Hence, its basicity is 3.

Answer 2

\[\ce{H3PO4}\] -

\[\begin{array}{cc}
\ce{O}\\
||\\
\ce{P}\\
/\phantom{...}|\phantom{...}\backslash\\
\ce{HO}\phantom{...}\ce{OH}\phantom{..}\ce{OH}
\end{array}\]

Since there are three OH groups present in H₃PO_4, its basicity is three i.e., it is a tribasic acid.