week acid-calculate the pH of a 0.0125M solution of HOCL
To calculate the pH of a solution of HOCl, we need to use the dissociation constant (Ka) of HOCl. The dissociation reaction of HOCl can be represented as follows:
HOCl ⇌ H+ + OCl-
The Ka expression for this reaction is:
Ka = [H+][OCl-] / [HOCl]
Given the concentration of HOCl as 0.0125 M, we can assume that the concentration of [H+] and [OCl-] is approximately the same since they are formed in a 1:1 ratio. Thus, we have:
[HOCl] = 0.0125 M
[H+] = [OCl-] = x (concentration of H+ and OCl-)
Substituting these values into the Ka expression:
Ka = x * x / 0.0125
Since the concentration of [H+] and [OCl-] is x, we can simplify the equation to:
Ka = x^2 / 0.0125
Now, we need to find the value of x that satisfies the equation. To do this, we can look up the value of Ka for HOCl, which is 3.5 x 10^-8. Using this Ka value:
3.5 x 10^-8 = x^2 / 0.0125
Simplifying the equation further:
x^2 = 3.5 x 10^-8 * 0.0125
x^2 = 4.375 x 10^-10
Taking the square root of both sides:
x ≈ 6.61 x 10^-6
This value represents the concentration of [H+] (and [OCl-]) in the solution. To calculate the pH, we can use the equation:
pH = -log10([H+])
pH = -log10(6.61 x 10^-6)
pH ≈ 5.18
Therefore, the pH of a 0.0125 M solution of HOCl is approximately 5.18.