Answer:
Ka = 1.5 × 10⁻⁵
Explanation:
Butyric acid is a weak acid that ionizes according to the following equation:
CH₃-CH₂-CH₂-COOH(aq) ⇄ CH₃-CH₂-CH₂-COO⁻(aq) + H⁺(aq)
We can find the value of the acid dissociation constant (Ka) using the following expression:
[tex]Ka=\frac{[H^{+}]^{2} }{Ca}[/tex]
where
[H⁺] is the molar concentration of H⁺
Ca is the initial molar concentration of the acid
We can find [H⁺] from the pH.
pH = -log [H⁺]
[H⁺] = antilog -pH = antilog -2.71 = 1.95 × 10⁻³ M
Then,
[tex]Ka=\frac{(1.95 \times 10^{-3})^{2} }{0.25} =1.5 \times 10^{-5}[/tex]
