Respuesta :
Answer:
a. pH = 5.22
b. Acidic.
c. pH = 5.14
Explanation:
a. It is possible to find the pH of a buffer using Henderson-Hasselbalch equation (H-H equation):
pH = pKa + log₁₀ [A⁻] / [HA]
Where pKa is -log Ka (For acetic acid = 4.74), [A⁻] is molar concentration of conjugate base (Acetate salt) and [HA] concentration of the weak acid (Acetic acid).
Replacing:
pH = 4.74 + log₁₀ [0.600M] / [0.200M]
You use the concentration of the acetic acid and sodium acetate because you're adding equal volumes, doing the ratio of the species the same
pH = 5.22
b. As the solution has a pH lower that 7.0, it is considered as a acidic solution.
c. When you add HCl to the buffer, the reaction is:
CH₃COO⁻ + HCl → CH₃COOH + Cl⁻
Where acetate ion reacts with the acid producing acetic acid.
As you have 0.200L of the buffer, 0.100L are of the acetate ion and 0.100L of the acetic acid. Initial moles of both compounds and moles of HCl added are:
CH₃COO⁻: 0.100L ₓ (0.600mol / L) = 0.0600 moles
CH₃COOH: 0.100L ₓ (0.200mol / L) = 0.0200 moles
HCl: 3.0mL = 3x10⁻³L ₓ (0.034mol / L) = 0.00010 moles HCl
The moles added of HCl are the same moles you're consuming of acetate ion and producing of acetic acid. Thus, moles after the reaction are:
CH₃COO⁻: 0.0600 moles - 0.0001 moles = 0.0509 moles
CH₃COOH: 0.0200 moles + 0.0001 moles = 0.0201 moles
Replacing in H-H equation:
pH = 4.74 + log₁₀ [0.0509moles] / [0.0201moles]
pH = 5.14
(a) The pH of the solution is 5.22
(b) The solution is Acidic
(c) The pH of the resultant solution is 5.14
Henderson-Hasselbalch Equation:
(a) The pH of a buffer can be calculated by using (H-H equation):
pH = pKa + log₁₀ [A⁻] / [HA]
Where pKa is -log Ka (for acetic acid = 4.74),
[A⁻] is the molar concentration of Acetate salt, and
[HA] concentration of the Acetic acid
According to the question:
pH = 4.74 + log₁₀ [0.600M] / [0.200M]
pH = 5.22
(b) The pH of the solution is lower than 7.0, therefore it is an acidic solution.
(c) After adding HCl to the buffer, the reaction is:
CH₃COO⁻ + HCl → CH₃COOH + Cl⁻
We have 0.200L of the buffer, 0.100L are of the acetate ion and 0.100L of the acetic acid.
The initial amount of compounds added are:
CH₃COO⁻: 0.100L ₓ (0.600mol / L) = 0.0600 moles
CH₃COOH: 0.100L ₓ (0.200mol / L) = 0.0200 moles
HCl: 3.0mL = 3x10⁻³L ₓ (0.034mol / L) = 0.00010 moles HCl
The HCl reacts with the same amount of acetate ion and produces acetic acid. Thus, moles after the reaction are:
CH₃COO⁻: 0.0600 moles - 0.0001 moles = 0.0509 moles
CH₃COOH: 0.0200 moles + 0.0001 moles = 0.0201 moles
From the H-H equation:
pH = 4.74 + log₁₀ [0.0509moles] / [0.0201moles]
pH = 5.14
Learn more about H-H equation:
https://brainly.com/question/26746644?referrer=searchResults
