Question

Why basicity of ${\mathrm{H}}_3{\mathrm{PO}}_3$ and ${\mathrm{H}}_3{\mathrm{PO}}_2$ are $2$ and $1$ respectively?

Answer 1

Basicity:

• An acid can be neutralized by a base, which can receive hydrogen ions from water.
• A molecule's basicity is determined by how well it can receive a proton $\left({\mathrm{H}}^{+}\right)$ and produce a stable end product.

Phosphorous acid - ${\mathrm{H}}_3{\mathrm{PO}}_3$:

• Phosphorous acid, commonly known as phosphonic acid, is an oxyacid of phosphorus that is colorless.
• The most important phosphorus oxygen acid, phosphoric acid, also known as orthophosphoric acid $\left({\mathrm{H}}_3{\mathrm{PO}}_4\right)$, was used to create fertilizer phosphate salts.
• Additionally, it is utilized in the production of albumin derivatives, dental cement, sugar, and textile products.
• In ${\mathrm{H}}_3{\mathrm{PO}}_3$ two types of bonds are present, one is $\mathrm{P}-\mathrm{OH}$ bond and the other is $\mathrm{P}-\mathrm{H}$ bond.

Figure: Phosphorous Acid

• The electronegative element oxygen is directly bonded to the two hydrogen atoms.
• As a result, phosphoric acid or orthophosphorous acid has a basicity of $2$.

Hypophosphorous acid - ${\mathrm{H}}_3{\mathrm{PO}}_2$:

• A phosphorus oxoacid is made up of single pentavalent phosphorus that is covalently connected to two hydrogen atoms, a hydroxyl group, two hydrogens, and an oxygen by single bonds to each of these groups.
• With the chemical formula ${\mathrm{H}}_3{\mathrm{PO}}_2$ , phosphinic acid, also known as hypophosphorous acid (HPA), is a potent reducing agent and phosphorus oxyacid.
• It is a colorless, low-melting substance that is soluble in alcohol, water, and dioxane.
• In ${\mathrm{H}}_3{\mathrm{PO}}_2$ also two types of bonds are present, one is $\mathrm{P}-\mathrm{OH}$ bond and the other is $\mathrm{P}-\mathrm{H}$ bond.

Figure: Hypophosphorous Acid

• The electronegative element oxygen is directly bonded to one hydrogen atom.
• As a result, phosphoric acid or orthophosphorous acid has a basicity of $1$.