In the strong acid-weak base titration, 0.1 M ammonium hydroxide ( NH4OH ) was titrated with 0.1 M hydrochloric acid ( HCl ). 2 drops of phenolphthalein were added as indicator into the conical flask which contains 25mL of hydrochloric acid, the mixture in the conical flask was colourless. Ammonium hydroxide was then titrated slowly into the conical flask and the conical flask was swirled gently to ensure complete reaction between the strong acid and weak base. The titration stops when the colour of the titrand changed from colourless to pale pink. The average titrant (29.55 mL) of 0.1 M of ammonium hydroxide was added into the conical flask. Phenolphthalein was then replaced by screened methyl orange as an indicator, the initial colour of the mixture in the conical flask was red. The average titre of (26.45 mL) of 0.1 M of ammonium hydroxide was added to change the colour of the titrand from red to grey in conical flask.

In weak acid-strong base titration, 0.1 M sodium hydroxide ( NaOH ) was titrated with 0.1 M acetic acid (CH3COOH). 2 drops of phenolphthalein indicator were added into the conical flask which contains 25mL of acetic acid. Sodium hydroxide was then titrated slowly into conical flask and the conical flask was swirled gently to ensure the reaction is reacted completely. The titration stops when the colour of the titrand changed from colourless to pale pink. The average titrant (28.60 mL) of 0.1 M of sodium hydroxide was added into conical flask. By using screened methyl orange as indicator, the average titrant (2.20 mL) of 0.1 M of sodium hydroxide was added to change the colour of titrand from red to grey in the conical flask.

In experiment part II (A), pH titration curve in the strong acid-weak base titration indicates that the initial pH value of the titrand is pH 1.33. The low initial pH value is due to the strong acid, 0.1 M hydrochloric acid ( HCl ). During the titration, the pH value increases steadily but not significant as the buffer solution is being built up, when extra base was added into the acid which can resist pH change. It increases to pH 2.94 after 25.00 mL of ammonium hydroxide was added. However, the pH value increases greatly from 3.59 to 5.99 when added extra 0.50mL of ammonium hydroxide as shown in the Graph 1.1. The pH values increase slowly as extra ammonium hydroxide was added. The equivalence point, which is the steepest point of graph, is pH 4.79.

In experiment part II (B), pH titration curve in the weak acid-strong base titration illustrates that the initial pH value of the titrand is pH 2.32, the pH is higher due to the weak acid, 0.1 M acetic acid. The pH value rises progressively due to the presence of buffer solution. The changes in pH values are small even when extra base was added. It increases to pH 7.00 after 26.00 mL of sodium hydroxide was added. The pH rises from 9.03 to 10.08 as another 0.5mL of sodium hydroxide was added. Based on the Graph 1.2, the equivalence point, which is the steepest point of graph, is pH 9.915.