For Part ?, experiment A where the reaction between NH4OH and HCl took place for phenolphthalein, 29.35mL of NH4OH was needed for phenolphthalein to detect the end point of the reaction with HCl. As for screened methyl orange, 25.70mL of NH4OH was needed for indicator to detect the end point with HCl. By comparing these results with Part ? A, where the titration curve showed the equivalence point of 27.00mL with pH 5.22, screened methyl orange was concluded as the suitable indicator for the reaction between strong acid and weak base as the average titre of titrant on second indicator was closer to the titrant volume mentioned for equivalence point. Moreover, the pH in equivalence point was also in the pH range of screened methyl orange, which was pH 3.1 to 4.4.
For Part ?, experiment B where average titre of 25.40mL of NaOH was needed for phenolphthalein to detect the end point of the reaction with CH3COOH in the reaction and 4.40mL of NaOH required for screened methyl orange to detect the end point with CH3COOH. After comparing with the titration curve at Part ? B, phenolphthalein was chosen as the most suitable indicator in the reaction between weak acid and strong base. This is due to the fact that the average titre volume of titrant was closer to the volume titrant in equivalence point, which was 26.50mL. Furthermore, the pH value of equivalence point from the titration curve, pH 9.08 was within the pH range of phenolphthalein, which was pH 8.3 to 10.0.