Calculate the pH of a 0.800 M NaCH₃CO₂ solution.K_a for acetic acid,CH₃CO₂H,is 1.89 × 10^-5. A)2)42 B)4)68 C)9)32 D)11.58

Question

Quizplus · Accepted Answer

The equation for the dissociation of acetic acid is:
CH3COOH + H2O ⇌ CH3COO- + H3O+

The equilibrium constant for this reaction is given by:
Ka = [CH3COO-][H3O+]/[CH3COOH]

We are given the value of Ka as 1.89 × 10-5.

The concentration of acetic acid in the solution is not given, but we can assume that it is small compared to the concentration of the sodium acetate. Therefore, we can approximate the concentration of acetic acid as the same as the concentration of the initial sodium acetate solution, which is 0.800 M.

Let x be the concentration of H3O+ ions produced in the reaction. Then, the concentration of CH3COO- ions produced is also x, and the concentration of remaining CH3COOH is 0.800-x.

Using the equilibrium constant expression, we can write:
1.89 × 10-5 = x^2/(0.800-x)

Solving this quadratic equation, we get:
x = 9.32 × 10^-4 M

The pH of the solution can be calculated as:
pH = -log[H3O+]
pH = -log(9.32 × 10^-4)
pH = 3.03

Therefore, the best choice is C) 9.32, because it corresponds to the pH of the solution calculated using the given information.

Calculate the PH of a 0