Predict whether the equivalence point of each of the following titrations is below, above, or at pH 7: Pyridine titrated with nitric acid
Look at what you have.
A strong acid + a weak base gives a salt that hydrolyzes to produce an acidic solution.
A weak acid and a strong base produces a salt that hydrolyzes to produce a basic solution.
A weak and and a weak base produces a salt that may be acidic, basic, or neutral depending upon the strengths of the weak acid and weak base. For these I remember (H^+) = sqrt(KwKa/Kb)
To predict whether the equivalence point of a titration is below, above, or at pH 7, we need to first understand the nature of the reactants involved.
Pyridine is a weak base, while nitric acid is a strong acid. When a strong acid reacts with a weak base, the resulting solution will be acidic. Therefore, the pH of the solution during the titration will be below 7.
During a titration, the equivalence point is reached when the moles of the acid and base are stoichiometrically equivalent. In this case, when all the pyridine has reacted with the nitric acid. At this point, all the pyridine is converted into its conjugate acid, which is a pyridinium ion.
Since the resulting solution from the reaction is acidic, the pyridinium ion will act as an acid and donate a proton, leading to a decrease in pH. Therefore, the equivalence point of the pyridine titrated with nitric acid will be below pH 7.
In summary, the equivalence point of the pyridine titration with nitric acid is below pH 7.