Question

Consider the titration of a 24.0 mL sample of 0.110 molL−1 CH₃COOH (Ka=1.8×10−5) with 0.125 molL−1 NaOH

Determine each quantity:

The initial pH

Answer 1

To find the initial pH of a 24.0 mL sample of 0.110 molL−1 CH₃COOH, we can use the equilibrium expression for the dissociation of acetic acid and the equation for pH as -log[H₃O⁺].

Step-by-step explanation:

The initial pH of a solution can be determined by considering the concentration of H+ ions present in the solution. In this case, we are given a 24.0 mL sample of 0.110 molL−1 CH₃COOH (acetic acid) and we need to find the initial pH before any titration occurs with NaOH. Acetic acid is a weak acid, and its dissociation in water can be represented by the equation:

CH₃COOH + H₂O ⇌ CH₃COO⁻ + H₃O⁺

The equilibrium expression for this reaction is given by: Ka = [CH₃COO⁻][H₃O⁺] / [CH₃COOH]

Since acetic acid is a weak acid, we can assume that its initial concentration is equal to its equilibrium concentration. Therefore, the concentration of [H₃O⁺] is equal to the concentration of [CH₃COOH]. Therefore, the initial pH can be calculated using the equation: pH = -log[H₃O⁺] . By substituting the given values, we can calculate the initial pH.