This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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Here are the solutions to the questions: ii) Phenolphthalein is a weak acid indicator. In acidic solutions, the equilibrium HIn(aq) H^+(aq) + In^-(aq) shifts to the left, and the indicator exists predominantly in its undissociated, colourless form (HIn). As a base is added during the titration, H^+ ions are neutralized, causing the pH to increase. At the end point, when the solution becomes slightly alkaline (pH 8.2-10), the equilibrium shifts to the right. The HIn dissociates to form In^-, which is the red/pink coloured form. This shift causes the solution to change from colourless to red/pink. iii) Phenolphthalein is suitable for titrations where the equivalence point occurs in the pH range of 8.2 - 10. This is characteristic of a titration between a weak acid and a strong alkali. Acid: Ethanoic acid* (CH_3COOH) Alkali: Sodium hydroxide* (NaOH) iv) To calculate the pH of the solution: Step 1: Calculate the pOH from the given OH^- ion concentration. [OH^-] = 0.0025 M pOH = -_10[OH^-] pOH = -_10(0.0025) pOH ≈ 2.60 Step 2: Calculate the pH using the relationship pH + pOH = 14. pH = 14 - pOH pH = 14 - 2.60 pH = 11.40