Determining the Acid Dissociation Constant of Boric Acid
How can we calculate the acid dissociation constant Ka of boric acid?
Given that the pH of a 0.13M solution of boric acid H3BO3 is measured to be 5.06. What steps do we need to take to determine Ka?
Calculation of Acid Dissociation Constant Ka of Boric Acid
First, let's establish the equilibrium expression for the dissociation of boric acid:
Ka = [H+][B(OH)3] / [H3BO3]
From the pH value of 5.06, we can determine the concentration of hydrogen ions [H+].
Using the formula [H+] = 10^(-pH), we find [H+] = 10^(-5.06).
Since the dissociation of boric acid is limited, the concentration of [B(OH)3] is approximately equal to [H+]. Thus, [B(OH)3] ≈ 10^(-5.06) M.
The concentration of H3BO3 is given as 0.13 M.
By substituting these values into the equilibrium expression, we obtain:
Ka = (10^(-5.06))^2 / 0.13 ≈ 5.7 x 10^(-10)
Therefore, the acid dissociation constant (Ka) of boric acid is 5.7 x 10^(-10).
Understanding the Acid Dissociation Constant Ka of Boric Acid
The acid dissociation constant (Ka) represents the extent to which an acid dissociates in water. In the case of boric acid (H3BO3), a weak acid, the Ka value of 5.7 x 10^(-10) indicates that it undergoes limited dissociation.
When boric acid is dissolved in water, it can partially dissociate into hydrogen ions (H+) and the conjugate base [B(OH)3]. The equilibrium expression, Ka, is a measure of this dissociation process.
By calculating the Ka of boric acid, we can understand its behavior in solution and its ability to donate protons. The value of Ka helps determine the strength of an acid and its tendency to donate hydrogen ions.
Overall, the process of determining the acid dissociation constant Ka provides valuable insights into the chemical properties of boric acid and its behavior in aqueous solutions.