PROCEDURE Safety Precautions: Sodium hydroxide and Acids are corros and will damage your skin and eyes. To perform the experiment, a pH sensor will be placed in the acid solution. The pH sensor is used to monitor pH as the titration with sodium hydroxide is performed Record the pH values and corresponding volume (mL) of NaOH added. Enough data points will have to be generated to obtain a smooth curve. In some regions of the titration, the pH will change very slowly, and larger increments of base, mL, can be added. Near the equivalence point (before and after), the pH changes very quickly, and the NaOH should be added dropwise. The subsequent pH reading should be recorded after the addition of each quantity of NaOH. The titration setup is shown in Figure 3. Center the beaker and the stir-bar on the stir-plate. Clamp the pH probe such that the tip and ball are submerged below the surface of the solution but, not touching the bottom. Allow sufficient clearance to allow the stir bar to spin freely 1. 150 mL beakers can be used to transport reagents from standardized bottles. This will avoid cross- contamination of the standardized bottles Obtain approximately 15 mL of the standardized hydrochloric acid, solution, approximately 15 mL of the standardized acetic acid solution, and approximately 75 mL of the standardized sodium hydroxide solution in separate beakers. Use the lab tape and markers to label beakers. Beakers should be covered with a watch glass when they're not in use 2. Record the concentrations of the HCI, CH3COOH, and NaOH solutions, which are on the reagent bottles, in the laboratory notebook. 3. Obtain a magnetic stir plate and a ring stand with a burette clamp and a small 3-finger clamp Figure 3. Titration setup 4. Clean and rinse a 25 mL burette. This burette will be used to dispense the NaOH. The lab team should discuss and decide on the appropriate material to use for the final rinse. If air bubbles appear in the tip of the burette, aggressively tap the burette to dislodge the bubbles. If bubbles continuously reappear then the burette has a small leak and the valves need to be serviced (discuss this with the lab instructor). TITRATION OF HCL 5. Measure 100.0 mL of DI water with a 100.0 mL graduated cylinder and pour it into a 250 mL beaker. Use a pipette to add 10.00 mL of the standardized acid solution into the same 250 mL beaker and add 2-3 drops of phenolphthalein indicator. Place the Teflon Stir Bar in the beaker carefully. General Chemistry 2