Question
Determine the pH of 0.30 M acetic acid with the ka of 1.8×10-⁵
Answers
GPT 3.5
To determine the pH of a solution containing acetic acid, we first need to calculate the concentration of hydronium ions (H3O+) in the solution.
The formula for the dissociation of acetic acid (CH3COOH) is as follows:
CH3COOH + H2O ⇌ CH3COO- + H3O+
The equilibrium constant (Ka) for this reaction is given as 1.8×10^-5. Since the initial concentration of acetic acid is 0.30 M, we assume that the initial concentrations of CH3COO- and H3O+ are both 0 M.
Let x be the concentration of H3O+ ions formed in the solution. At equilibrium, the concentrations of CH3COO- and H3O+ ions both equal x. The concentration of CH3COOH will be 0.30 - x.
Using the equilibrium constant expression for the dissociation of acetic acid, Ka = [CH3COO-][H3O+]/[CH3COOH], we can substitute the concentrations at equilibrium to get:
1.8×10^-5 = (x)(x)/(0.30 - x).
Since x is much smaller than 0.30, we can make the approximation that 0.30 - x ≈ 0.30. We can then solve for x:
1.8×10^-5 = (x)(x)/(0.30),
x^2 = 1.8×10^-5 * 0.30,
x = sqrt(1.8×10^-5 * 0.30).
Now we have the concentration of H3O+ ions, and to find the pH of the solution, we can calculate the negative logarithm of this concentration:
pH = -log[H3O+].
Substitute the value of x into the expression to find the pH of the solution.
The formula for the dissociation of acetic acid (CH3COOH) is as follows:
CH3COOH + H2O ⇌ CH3COO- + H3O+
The equilibrium constant (Ka) for this reaction is given as 1.8×10^-5. Since the initial concentration of acetic acid is 0.30 M, we assume that the initial concentrations of CH3COO- and H3O+ are both 0 M.
Let x be the concentration of H3O+ ions formed in the solution. At equilibrium, the concentrations of CH3COO- and H3O+ ions both equal x. The concentration of CH3COOH will be 0.30 - x.
Using the equilibrium constant expression for the dissociation of acetic acid, Ka = [CH3COO-][H3O+]/[CH3COOH], we can substitute the concentrations at equilibrium to get:
1.8×10^-5 = (x)(x)/(0.30 - x).
Since x is much smaller than 0.30, we can make the approximation that 0.30 - x ≈ 0.30. We can then solve for x:
1.8×10^-5 = (x)(x)/(0.30),
x^2 = 1.8×10^-5 * 0.30,
x = sqrt(1.8×10^-5 * 0.30).
Now we have the concentration of H3O+ ions, and to find the pH of the solution, we can calculate the negative logarithm of this concentration:
pH = -log[H3O+].
Substitute the value of x into the expression to find the pH of the solution.