How to Calculate Hydronium Ion Concentration and pH in Acetic Acid Solution

[Fiza43]

a student prepared a 0.10 M solution of acetic acid, CH3COOH. acetic acid has a Ka of 1.75 * 10^-5. what are the hydronium ion concentration and the pH of the solution?

[hydronium ion] =
pH =

 

[chemisttree]

Write out the expression for Ka and substitute what you know into the expression.

 

[Blueshift5]

To calculate the hydronium ion concentration and pH in an acetic acid solution, we first need to understand the properties of acetic acid. Acetic acid is a weak acid, meaning it does not completely dissociate in water. This means that not all of the acetic acid molecules will break apart into ions. Instead, a portion of the acetic acid will remain in its molecular form, while the rest will dissociate into hydronium ions (H3O+) and acetate ions (CH3COO-).

To find the hydronium ion concentration, we can use the equation:
Ka = [H3O+][CH3COO-]/[CH3COOH].
Since we know the value of Ka for acetic acid (1.75 * 10^-5) and the initial concentration of acetic acid (0.10 M), we can rearrange the equation to solve for [H3O+].
[H3O+] = Ka * [CH3COOH]/[CH3COO-]
= (1.75 * 10^-5) * (0.10 M)/(1.00 M)
= 1.75 * 10^-6 M

Therefore, the hydronium ion concentration in the 0.10 M acetic acid solution is 1.75 * 10^-6 M.

To find the pH of the solution, we can use the equation:
pH = -log[H3O+].
Plugging in the [H3O+] value we calculated above, we get:
pH = -log(1.75 * 10^-6)
= 5.76

Therefore, the pH of the 0.10 M acetic acid solution is 5.76. This indicates that the solution is slightly acidic, as a pH of 7 is considered neutral.

In conclusion, to calculate the hydronium ion concentration and pH in an acetic acid solution, we can use the Ka value and initial concentration of the acid. It is important to note that these calculations assume ideal conditions and may vary slightly in a real-life scenario.