Answer:
pH = 5.54
Explanation:
We can think of the pyridinium cation as a weak acid (of pKa 5.25), and of pyridine as its conjugate base. As such, we can use the Henderson-Hasselbach equation to solve this problem:
pH = pKa + log ( [Pyridine]/[Pyridinium] )
pH = 5.25 + log (0.59/0.30)
pH = 5.25 + 0.29
pH = 5.54
