Question

why do weak acid with different concentrations have similar buffering region?

Answer 1

Sol:

Definitions:

According to the theory proposed by the Bronsted-Lowery, the acid is any substance that can donate the proton to the other substances and base is any substance that can accept the proton from the acid.

pH of the solution is nothing but the negative logarithm of the concentration of hydrogen ions in the aqueous solution.

An acid that ionizes or dissociates partially when dissolved in water is known as a weak acid.

buffering solutions are those solutions which contains weak acid and salt of weak acid with strong base or weak base and salt of weak base with strong acid.

This buffering solutions maintains the pH of the solution and neutralizes the added excessive hydrogen ion concentration in the solution.

Explanation:

when the acids with different concentrations is added to the solution the conjugate base of the weak acids will absorb the proton donated by the acid and thus results in no effective change in pH.

The strong acids are dissociate completely in the solution but in case of weak acids they dissociates partially. When an weak acids dissociate in solution it have both a dissociated state (A^-) and undissociated state (AH) that present in the solution as follows:

$AH\rightleftharpoons A^{-} + H^{+}$

As per the above dissociation equation the concentration of undissociated acid and dissociated acid remains the same.

The dissociation equation for weak acids is as follows:

$K_{a} = \frac{[]A^{-}][H^{+}]}{[AH]}$

The square brackets indicate the concentration of respective components.

from the dissociation equation it will be seen that the weak acids with different concentration has the nearly same value of dissociation constant.

The value of dissociation constant directly related to the release of the proton.

From the above discussion, it will be concluded that the weak acid with different concentrations have nearly similar value of dissociation constant and thus results in similar buffering region.