Question

When $CH_3COOCH_3 + HCl$ is titrated with $NaOH$ then at neutral point the colour of phenolphthalein becomes colourless from pink due to

• A. formation of $CH_3OH$
• B. formation of $CH_3COOH$ which acts as a weak acid
• C. phenolphthalein vaporizes
• D. presence of $HCl$

Answer 1

Answer: (B)

formation of $CH_3COOH$ which acts as a weak acid

Answer 2

NaOH solution is taken in a conical flask with phenolphthalein indicator (pink colour) and CHCOOCH + HCl solution is added from burette slowly. First, HCl left after hydrolysis of ester (being a strong acid) gets consumed then CHCOOH being a weak acid will bring the titration to the neutralisation point. ${CH3COOCH3 ->[H_2O][H^+] CH3COOH + CH3OH}$ ${HCl + NaOH -> NaCl + H2O}$ ${CH3COOH + NaOH ->CH3COONa }$