Procedure: 1. Pipette 25 cm3 of ethanoic acid into a conical flask 2. Titrate against 0.1M sodium hydroxide solution in the burrette, using phenolphthalein as indicator. 3. Pipette further 25 cm3 of ethanoic acid into the solution after titration and mix throughly. Questions: 1. what is the retionship between pH and Ka 2. Is it important that the titre (volume of sodium hydroxide solution) should be exactly25cm3? 3. What is the purpose of adding a further portion of ethanoic acid to the solution after titration? 4. A student prepare 2 buffer solution Buffer A : 0.5M ethanoic acid + 0.5M sodium ethanoate salt in equal volume Buffer B : 5M ethanoic acid + 5M sodium ethanoate salt in equal volume Do you think which is a good buffer? Why? 5. what discussion can be made on this experiment?