Why Does H3PO2 Have a Basicity of 1?

[Saitama]

Basicity is 1??

I was studying about Volumetric Analysis. In the chapter, there is a table which shows basicity of some acids. One is H₃PO₂. Its basicity is given as 1. But basicity of an acid is number of replacable hydrogen atoms present in one molecule of acid. So, bascitiy of H₃PO₂ should be 3. But that's not true according to book. It is 1.

 

[epenguin]

I was studying about Volumetric Analysis. In the chapter, there is a table which shows basicity of some acids. One is H₃PO₂. Its basicity is given as 1. But basicity of an acid is number of replacable hydrogen atoms present in one molecule of acid. So, bascitiy of H₃PO₂ should be 3. But that's not true according to book. It is 1.

You'd be right if you were talking about H₃PO₃.

 

[Saitama]

You'd be right if you were talking about H₃PO₃.

But why is its basicity 1?

 

[epenguin]

It looks like you are just confusing phosphoric acid where 3 H's are attached via O with hyopophorous acid where two H's are attached to P.

http://en.wikipedia.org/wiki/Hypophosphorous_acid

You are a lot less likely to ever meet the second, you are full enough of the first and esters and anhydrides of it in a very dynamic state.