Final answer:
The pKa of acetic acid, given the pH and molarities of acetic acid and sodium acetate in a buffer solution, can be calculated using the Henderson-Hasselbalch equation.
Step-by-step explanation:
To determine the pKa of acetic acid when the pH of a solution that is 0.25 molar in acetic acid and 0.1 molar in sodium acetate is 4.36, we can use the Henderson-Hasselbalch equation:
pH = pKa + log([A-]/[HA])
Where [A-] represents the molarity of the acetate ion and [HA] is the molarity of acetic acid. In this case, we rearrange the equation to solve for pKa:
pKa = pH - log([A-]/[HA])
pKa = 4.36 - log(0.1/0.25)
pKa = 3.9621
By calculating this equation, we can find the pKa value for acetic acid. Considering the given concentrations correspond to a buffer system, the pKa can be directly related to the buffer's pH.