Question

Is there any formula for calculating the basicity of an acid? If no, how else can we calculate the basicity of an acid?

Answer 1

if you 've found pH of acid then subtract that from 14 which explain basicity of acid........for ex
if pH of an acid is 2 then its basicity is 14-2=12

Answer 2

HELLO THERE!

Basicity is basically the number of replaceable Hydrogen atoms present in an acid, that can be replaced by a metal ion or ammonium ion.

Or, when water is added to an acid, the number of hydronium ions that is produced per molecule of the acid is it's basicity.

Or, the number of types of salts that are formed from the acid when it reacts with a base also determines it's basicity.

Consider Sulphuric acid as an example:

From it's formula, H₂SO₄, we can see that it has two hydrogen atoms, both of which can be replaced by a metal or ammonium.

[Note: Acetic acid, CH₃COOH has four H atoms, but it's not tetrabasic, it's monobasic. This is because only the last Hydrogen (of OH) group can be replaced by a metal or ammonium].

It's dissociation in water:

H₂SO₄ + H₂O -------> H₃O⁺ + HSO₄⁻

HSO₄⁻ + H₂O ---------> H₃O⁺ + SO₄²⁻

We get two hydronium ions for one molecule of the acid, hence sulphuric acid is a dibasic acid.

It's salt formation when it reacts with Sodium Hydroxide:

H₂SO₄ + NaOH --------> NaHSO₄ + H₂O (acidic salt is formed due to partial displacement).

H₂SO₄ + 2NaOH ------> Na₂SO₄ + 2H₂O (normal salt is formed due to complete displacement).

Since it can produce two types of salt, acidic salt and normal salt, we can say that it's basicity is two.

So, what you must know to find out the basicity of an acid is that, you must know how to dissociate the acid, step by step, forming all possible ions.

THANKS!