Final answer:
To calculate the pH during the titration of a weak base with a strong acid, we consider the reaction that occurs. The concentration of the weak base decreases as the concentration of the conjugate acid increases. The pH can be calculated using the equilibrium constant expression for the weak base reaction.
Step-by-step explanation:
To calculate the pH during the titration of a weak acid and strong base, we need to consider the reaction that occurs. In this case, (CH₃)₂NH is a weak base and HI is a strong acid. When a weak base reacts with a strong acid, the weak base is neutralized and the conjugate acid is formed. The conjugate acid of (CH₃)₂NH is (CH₃)₂NH₂⁺.
The reaction between (CH₃)₂NH and HI can be represented as:
(CH₃)₂NH + HI → (CH₃)₂NH₂⁺ + I⁻
As the titration progresses, the concentration of (CH₃)₂NH decreases, and the concentration of (CH₃)₂NH₂⁺ increases. The pH can be calculated by using the equilibrium constant expression for the weak base reaction:
Kb = [CH₃)₂NH₂⁺][OH⁻] / [CH₃)₂NH]
Since HI is a strong acid, [H⁺] can be assumed to be equal to the initial concentration of HI.
Using the given information and the equation for Kb, you can calculate the pH after each volume of titrant has been added.