Question

Basicity of H3PO3 and H3PO2 is respectively:-

Answer 1

H3PO3 => O = P - H - OH - OH

As there are TWO OH bond,

So, Basicity = 2

Similarly, H3PO2 => O = P - H - OH - H

As there is only ONE OH bond.

So, the basicity = 1.

Thereforth, 2 and 1 (Option D)

Answer 2

Basicity of $H_{3} PO_{3}$ is 2.

Basicity of $H_{3} PO_{2}$ is 1.

A molecule's basicity refers to its capacity to take a proton ($H^{+}$) and generate a stable product.

Phosphorous acid $H_{3} PO_{3}$

Phosphorous acid is commonly known as phosphonic acid. It is a colourless phosphorus oxyacid.  

Basicity

There are two sorts of linkages in phosphorous acid that we can see.

Bonds between P-OH  bonds and P-H bond

The electronegative element oxygen is immediately linked to the two hydrogen atoms.

As a result, it has basicity of 2.

Hypophosphorous acid $H_{3} PO_{2}$

A phosphorus oxoacid is made up of single pentavalent phosphorus that is covalently connected to two hydrogens, a hydroxy group, and oxygen via single bonds.  

Basicity

We may see two different sorts of linkages in hypophosphorous acid.

Bonds between P-OH  bonds and P-H bond

The electronegative element oxygen is directly linked to only one hydrogen atom.

As a result, Hypophosphorous acid has basicity of 1.