A titration of 25.0 mL of a solution of the weak base aniline, C₆H₅NH₂, requires 25.67 mL of 0.175 M HCl to reach the equivalence point.

C₆H₅NH₂(aq) + H₃O⁺(aq) ⇄ C₆H₅NH₃⁺(aq) + H₂O(ℓ)

(a) What was the concentration of aniline in the original solution?

(b) What are the concentrations of H₃O⁺, OH⁻, and C₆H₅NH₃⁺ at the equivalence point?

(c) What is the pH of the solution at the equivalence point?

Interpretation:

For the titration between C6H5NH2 and HCl. The concentration of C6H5NH2 solution has to be calculated.

Concept introduction:

Titration is a quantitative method to determine the quantity of an acid or base in a solution.

For strong acid-weak base titration the pH value can be calculated at various points before and after equivalence point. The equilibrium established during the titration of C6H5NH2 with HCl is represented as,

C6H5NH2(aq)+ H3O+(aq)⇌H2O(l)+C6H5NH3+(aq)

Calculation of concentration is given below.

Given:

The concentration of HCl is 0.175 mol⋅L−1.

The volume of HCl used is 25.67 mL or 0.02567 L.

The volume of aniline titrated is 25 mL or 0.025 L.

The concentration of aniline is calculated as,

Expression used for the neutralization is as follows,

C1V1=C2V2

Here,

• C1 is the concentration of aniline.
• V1 is the volume of aniline.
• C2 is the concentration of HCl used.
• V2 is the volume of HCl used for the neutralization.

Substitute 0.02567 L for V2, 0.025 L for V1,0.175 mol⋅L−1 for C2

Interpretation:

For the titration between C6H5NH2 and HCl. The concentration of OH−,H3O+, and C6H5NH3+ is to be calculated at equivalence point has to be calculated.

Concept introduction:

Titration is a quantitative method to determine the quantity of an acid or base in a solution.

For strong acid-weak base titration the pH value can be calculated at various points before and after equivalence point. The equilibrium established during the titration of C6H5NH2 with HCl is represented as,

C6H5NH2(aq)+ H3O+(aq)⇌H2O(l)+C6H5NH3+(aq)

Interpretation:

For the titration between C6H5NH2 and HCl. The value of pH at equivalence point has to be calculated.

Concept introduction:

Titration is a quantitative method to determine the quantity of an acid or base in a solution.

For strong acid-weak base titration the pH value can be calculated at various points before and after equivalence point. The equilibrium established during the titration of C6H5NH2 with HCl is represented as,

C6H5NH2(aq)+ H3O+(aq)⇌H2O(l)+C6H5NH3+(aq)