Experiment 1: Perform a Coarse Titration 1. Take a burette and a 50 mL beaker from the Containers shelf and place them on the workbench. 2. Place the beaker underneath the burette as a waste container. 3. Obtain 0.100 M sodium hydroxide from the Materials shelf and add 52 ml to the burette. Click the stopcock of the buret repeatedly to drain liquid from the buret into the waste container until the titrant level is at or below the 0 mL mark. Double-click the buret to read and record the liquid volume at the meniscus. This is the total initial titrant volume in the burette. (This is to give you practice dispensing titrant from the buret. You can dump the beaker into the waster and place it in the sink once you have read your initial volume on the buret.) 4. Take a clean 50 mL graduated cylinder from the Containers shelf and place it on the workbench. 5. Take hydrochloric acid #1 (unknown concentration) from the Materials shelf and add 5.0 mL to the graduated cylinder. 6. Take water from the Materials shelf and add 15.0 mL to the graduated cylinder. This increases the total volume of the analyte, making it easier to see the color change. Please note that the value to use for the volume of hydrochloric acid when calculating its concentration is still 5.0 mL. 7. Obtain a 150 mL Erlenmeyer flask from the Containers shelf, and pour the liquid from the graduated cylinder into the flask. Take phenolphthalein from the Materials shelf and add 0.1 mL to the flask. 8. Move the Erlenmeyer flask onto the base of the burette. The Erlenmeyer flask is connected to the burette so that liquid will drip from the burette into the Erlenmeyer flask. 9. Click on the stopcock. One click will dispense one drop from the burette. The volume dispensed should be about 0.05 mL, which is most likely too small to notice using the burette markings. 10. Click and hold the stopcock for a few seconds. You should observe the volume in the buret decreasing rapidly as the liquid is dispensed. You want to add the titrant in approximately 2.00 mL increments. If the volume dispensed is above 2.50 mL, try holding the stopcock for a shorter period of time. 11. Continue to add titrant in approximately 2.00 mL increments. Pause after each dispensation. Record the volume dispensed. 12. When the reaction reaches the end point, the solution changes color. 13. Stop once you reach the end point. Record the volume dispensed before the end point as the final volume. You now know between which two volumes the end point occurred. (For example, if you recorded 12.00 mL before the end point, but 14.00 mL was past the end point, record the 12.00 mL as your final volume.) 14. Clear your station by emptying the containers into the waste, then placing the containers in the sink. Experiment 2: Perform a Fine Titration 1. Prepare a burette and Erlenmeyer flask as described in steps 1 - 7 in experiment 1. 2. Rapidly add titrant to the flask until you reach the final volume (before the end point) determined in the coarse titration. To do this, click and hold the stopcock for longer periods of time. The solution in the Erlenmeyer flask should still be colorless. 3. Add titrant one drop at a time. This can be tedious, but if you click and hold you might miss the exact end point of the titration. 4. When the solution in the Erlenmeyer flask changes color, stop adding titrant. Record the final volume of titrant dispensed. 5. Repeat the fine titration two more times. Your three dispensed volumes should agree within 0.04 mL. If they do not, repeat the fine titration until you have three close volumes. 6. Clear the bench of all materials, containers, and instruments, then go to Edulastic to complete the assignment for this lab. Experiment 1: Perform a Coarse Titration Record your results from the Coarse Titration in the following table. Item Measurement Dispensed Volume of 0.100 M NaOH (mL) co B I U = = = := = = = X, xº a *Note: This is the last Dispensed Volume BEFORE the solution in the flask changes color. (Dispensed Volume = Vf-V;)