Exp 5

• Using a pipet, transfer the required volume of concentrated HCI into a 500-mL volumetric flask containing 100 mL distilled water. Swirl.
• Cool the solution. Add distilled water into the flask until the liquid level reaches near the calibration mark. Adjust the volume to the flask's calibration mark using a dropper.

  Stopper the flask and shake.
• Obtain two (2) clean and dry 250-m Erlenmeyer flasks. Label them

  T1 and T2 respectively.
• Transfer 25 mL of your previously standardized NaOH using a pipet into the 2 labeled flasks. Cover the opening of the flask with a filter paper. Record the volumes in the report sheet.
• Rinse a 50-mL burette with tap water, then rinse it twice with distilled water. Make the final rinsing of the burette with about 3 mL of the HCl solution you just prepared and make certain that you drain it through the stopcock.
• At your lab table, add 2 drops of phenolphthalein indicator into NaOH 1. This will turn pink.
• On the report sheet below, record the initial reading of the HCI solution in the burette as 0.0 mL.
• Place a white sheet of paper under Erlenmeyer flask T1 to facilitate the detection of the end point when noting the color change of the indicator. Titrate NaOH solution 1 by slowly adding HCI from the burette and constantly swirling the flask until you have reached the end point. This is indicated by the first disappearance of the pink color of phenolphthalein. Take the final burette reading to the nearest 0.02 mL and record it on your report sheet.
• Titrate NaOH T2 using the same procedure as in steps 3-4; however, this time, record the initial reading of the HCI solution in the burette based on the actual reading, not0.0 mL. Transfer your HCI solution in a designated container, cover, and save for use in the following experiments.