The indicator used can change colors at different pH values. OBJECTIVE To determine the concentration of sulfuric acid (HOSTS) using titration technique CHEMICALS Noah solution, approximately 0. 2 M, dilute sulfuric acid of unknown malarial, phenolphthalein APPARATUS Burette. Burette clamp, retort stand, 20 ml volumetric pipette, pipette filter, 250 ml conical flask PROCEDURES 1) The burette was washed with distilled water and then rinsed with about 5-10 ml of Noah solution, running the second rinsing through the burette tip.
The burette was clamped to the retort stand 2) The burette was filled with the base, made sure the tip was completely filled and contain no air bubbles. The initial burette reading was recorded 3) Using a volumetric pipette, 20. 00 ml HOSTS was transferred to a clean 250 ml conical flask. 2 or 3 drops of phenolphthalein indicator was added. This flask was placed on a piece of white paper under the burette and the burette tip was lowered into the flask. The initial burette reading was recorded, to 2 decimal places ) The acid was titrated by adding base until the end point was reached.
During the titration, the flask was been swirl. The end point was indicated when the entire solution retain a faint pink color for at least 30 seconds. The final burette reading was recorded. This was the result of the rough titration 5) The process were repeated until two consecutive titration agree to В± O. 10 ml 6) The readings from all titration was recorded 7) When finished with the titration, the burette was emptied and rinsed at least wick with tap water and once with distilled water QUESTIONS 1.
Why is phenolphthalein used in the experiment ? The phenolphthalein was used in the experiment as an indicator to determine the end point of titration. Phenolphthalein can change colors at different pH values. When the phenolphthalein changes color from colorless to faint pink, the titration process was stopped immediately because it has reached the end point 2. Noah is a hygroscopic compound and all Noah solutions must be denaturized before it can be used for analysis.