Final answer:
To reach the equivalence point in titrating 2.65 L of 0.0750 M pyridine with 0.507 M HNO₃, 392.1 mL of HNO₃ is required, and the pH at the equivalence point would be approximately 0.295.
Step-by-step explanation:
To find the pH and the volume of 0.507 M HNO₃ needed to reach the equivalence point in the titration of 2.65 L of 0.0750 M pyridine, we need to calculate the moles of pyridine (C₅H₅N) and then find the moles of HNO₃ required to neutralize it.
First, calculate the moles of pyridine:
Moles of pyridine = 2.65 L × 0.0750 M = 0.19875 mol.
Since pyridine is a monoprotic base, it will react with an acid in a 1:1 molar ratio. Thus, the moles of 0.507 M HNO₃ needed would be equal to the moles of pyridine.
Now, calculate the volume of HNO₃ required:
Volume of HNO₃ = Moles of HNO₃ / Concentration of HNO₃
Volume of HNO₃ = 0.19875 mol / 0.507 M = 0.3921 L or 392.1 mL.
To calculate the pH at the equivalence point, we utilize the fact that HNO₃ is a strong acid and will completely dissociate, thus the concentration of H⁺ ions at the equivalence point will be equal to the concentration of HNO₃. Since the concentration is 0.507 M, the pH would be the negative log of the hydrogen ion concentration:
pH = -log(0.507) ≈ 0.295.