The chemical reaction for dissociation of an acid is:
HA + H2O → H3O+ + A-
Assuming all of the hydronium ion (calculated in in the previous problem) comes from this reaction, what is the concentration of conjugate base, [A-], in this system?
(H3O^+) = (A^-)
To determine the concentration of the conjugate base, [A-], we need to know the initial concentration of the acid, HA, and apply the principle of conservation of mass.
Let's assume the initial concentration of HA is denoted as [HA]₀.
According to the chemical reaction,
HA + H2O → H3O+ + A-
The reaction shows a 1:1 stoichiometry between HA and A-. This means that for every one molecule of HA that dissociates, one molecule of A- is produced. Since we are assuming all of the hydronium ions come from this reaction, we can say that the concentration of hydronium ions, [H3O+], is also equal to [HA]₀.
Therefore, [H3O+] = [HA]₀
Since [H3O+] = [HA]₀, and the reaction produces an equal concentration of hydronium ions and conjugate base, we can conclude that:
[A-] = [H3O+] = [HA]₀
So, the concentration of conjugate base, [A-], in this system is equal to the initial concentration of the acid, [HA]₀.
To determine the concentration of the conjugate base, [A-], we need to use the concept of stoichiometry. The equation for the dissociation of the acid indicates that for every one molecule of acid (HA) that dissociates, one molecule of conjugate base (A-) is formed.
The concentration of the conjugate base, [A-], is dependent on the concentration of the acid, [HA], and the extent of its dissociation.
Assuming all of the hydronium ion (H3O+) comes from this reaction, it means that the acid is completely dissociated. Therefore, the concentration of [H3O+] is equal to the initial concentration of the acid, [HA].
Now, since one molecule of acid (HA) dissociates to form one molecule of conjugate base (A-), the concentration of the conjugate base, [A-], is also equal to the initial concentration of the acid, [HA].
Therefore, the concentration of the conjugate base, [A-], in the system is equal to the initial concentration of the acid, [HA].