A 0.02M solution of pyridinium hydrochloride has pH = 3.44. Calculate the ionization constant of pyridine.
The ionization constant of pyridine is .
Explanation
Pyridinium hydrochloride is a salt of a weak base (pyridine) and a strong acid (HCl). In aqueous solution, the pyridinium ion hydrolyzes to produce ions, making the solution acidic. Using the pH, we first find the concentration. Then, applying the hydrolysis relation for a salt of a weak base and strong acid, , we can calculate the ionization constant () of the weak base pyridine.
Solution Steps
Step 1: Calculate the hydrogen ion concentration from the given pH.
M
Step 2: Write the hydrolysis reaction and the relation for . Pyridinium hydrochloride () is a salt of a weak base and a strong acid. The cation hydrolyzes as:
For this salt,
Step 3: Rearrange the formula to solve for .
Step 4: Substitute the known values into the equation. Given: M, , M
Step 5: Calculate the final value of .