What is the pH of solution formed by adding 25.0 mL of 0.100 M HCl to 25.0 mL of 0.100 M pyridine (C₅H₅N, K _b = 1.8×10^{- 9})?

Question

Quizplus · Accepted Answer

The first step is to write the balanced equation for the reaction between HCl and pyridine:

HCl + C5H5N -> C5H5NHCl

This reaction is an acid-base reaction where HCl is the acid and pyridine is the base. The pyridine will react with the H+ ions from HCl to form C5H5NH+ ions.

The next step is to calculate the initial moles of HCl and pyridine:

moles of HCl = 0.100 mol/L x 0.025 L = 0.0025 mol
moles of pyridine = 0.100 mol/L x 0.025 L = 0.0025 mol

Since the moles of HCl and pyridine are equal, the pyridine will be completely consumed in the reaction. This means that the moles of H+ formed will be equal to the moles of pyridine initially present:

moles of H+ = 0.0025 mol

Now we need to calculate the concentration of H+ ions in the solution. We know that the volume of the solution is 50.0 mL (25.0 mL HCl + 25.0 mL pyridine), so we can calculate the total moles of the solution:

moles of solution = 0.0025 mol H+ + 0.0025 mol pyridine = 0.0050 mol

Using the total volume of the solution, we can calculate the molarity of the H+ ions:

Molarity of H+ = moles of H+ / total volume of solution = 0.0050 mol / 0.050 L = 0.100 M

Finally, we can calculate the pH of the solution using the formula:

pH = -log[H+]

pH = -log(0.100) = 1 - (-1)log(0.100) = 1 + 1 = 2

Therefore, the answer is D) 3.28.

What Is the PH of Solution Formed by Adding 25