Calculate the pH for an aqueous solution of acetic acid that contains 2.15 × 10^-3 M hydronium ion. A)4.65 × 10^-12 B)2.15 × 10^-3 C)2.67 D)11.33

Question

Quizplus · Accepted Answer

Acetic acid is a weak acid and can be represented by the equation: 
CH3COOH + H2O ⇌ CH3COO- + H3O+
The acid dissociation constant (Ka) for acetic acid is 1.8 × 10^-5.
Therefore, we can use the equation for Ka to calculate the concentration of hydronium ion in the solution:
Ka = [CH3COO-][H3O+] / [CH3COOH]
1.8 × 10^-5 = (x)(2.15 × 10^-3) / (0.1 - x)
Where x is the concentration of hydronium ion in mol/L.
Solving for x gives x = 0.00466 M
The pH can be calculated using the formula pH = -log[H3O+].
Therefore, pH = -log(0.00466) = 2.67. 
Option C is correct.

Calculate the PH for an Aqueous Solution of Acetic Acid