You require 36.78 mL of 0.0105 M HCl to reach the...

You require 36.78 mL of 0.0105 M HCl to reach the equivalence point in the titration of 25.0 mL of aqueous ammonia. (a) What was the concentration of $\mathrm{NH}_{3}$ in the original ammonia solution? (b) What are the concentrations of $\mathrm{H}_{3} \mathrm{O}^{+}, \mathrm{OH}^{-},$ and $\mathrm{NH}_{4}^{+}$ at the equivalence point? (c) What is the pH of the solution at the equivalence point?

You require 36.78 mL of 0.0105 M HCl to reach the equivalence point in the titration of 25.0 mL of aqueous ammonia.
(a) What was the concentration of $\mathrm{NH}_{3}$ in the original ammonia solution?
(b) What are the concentrations of $\mathrm{H}_{3} \mathrm{O}^{+}, \mathrm{OH}^{-},$ and $\mathrm{NH}_{4}^{+}$ at the equivalence point?
(c) What is the pH of the solution at the equivalence point?

Key Concepts

Acid-Base Titration

Acid-base titration is an analytical technique used to determine the concentration of an acid or a base by reacting it with a titrant of known concentration. The titrant is added gradually until the reaction reaches the equivalence point, where the moles of acid equal the moles of base, allowing for precise stoichiometric calculations.

Equivalence Point

The equivalence point in a titration is reached when the stoichiometrically equivalent amounts of acid and base have reacted. This concept is crucial for calculating concentrations of the original solutions and for predicting the chemical composition of the solution after the reaction, such as the formation of a conjugate acid or base.

Stoichiometry and Molarity Calculations

Stoichiometry involves using balanced chemical equations to relate the amounts of reactants and products. Molarity calculations, which express concentration in moles per liter, allow one to determine the number of moles present in a given volume and are fundamental in titration analysis to find unknown concentrations.

Weak Base and its Conjugate Acid

When a weak base is titrated with a strong acid, the reaction forms its conjugate acid. Understanding the behavior of the weak base and its conjugate acid is essential, as the conjugate acid can affect the pH of the solution due to its tendency to donate protons (or undergo hydrolysis) in water.

Hydrolysis Equilibrium

Hydrolysis equilibrium refers to the reaction in which the conjugate acid (or base) of a weak base (or acid) reacts with water to re-establish an equilibrium, often producing hydronium (H3O+) or hydroxide (OH-) ions. This process is key to determining the pH of the solution at the equivalence point in a titration involving weak bases or weak acids.

pH Calculation in Weak Acid-Base Systems

The pH of a solution at the equivalence point in a titration involving a weak base and a strong acid is determined by the hydrolysis of the resulting conjugate acid. This pH calculation involves using the acid dissociation constant (Ka) of the conjugate acid, along with equilibrium expressions, to quantify the concentration of hydronium ions present in the solution.

Transcript

Please give Ace some feedback