Equipment:
- Data collection system - Clamp, right-angle
- Conductivity sensor - Clamp, buret
- Drop counter with micro stir bar - 0.0200 M H2SO4 solution, 50-mL
- Magnetic stirrer - Barium hydroxide (Ba(OH)2), unknown
concentration, 50-mL
- Buret, 50-mL - Deionized water, 50-mL
- Beaker (2), 100-mL - Wash bottle with deionized water
- Beaker, 50-mL - Cotton swab or tissue
-Volumetric pipet, 50-mL
- Ring stand
Methods:
1. Start a new experiment on the data collection system.
2. Connect the conductivity sensor to the data collection system.
3. Assemble the titration apparatus, using the steps below and the illustration as a guide:
a. Position the magnetic stirrer on the base of the ring stand.
b. Place a waste container (100-mL beaker) on the magnetic stirrer.
c. Use the buret clamp to attach the buret to the ring stand.
d. Position the drop counter over the waste container and attach it to the ring stand using the right-angle clamp.
e. Place the conductivity sensor through one of the slots in the drop counter(Do not connect the drop counter to the data collection system yet).
4. Rinse the buret with several milliliters of the standardized 0.0200 H2SO4 solution:
a. Ensure that the stopcock is closed and rinse the inside of the buret with several milliliters of the standardized H2SO4 solution.
b. Open the stopcock on the buret and drain the rinse H2SO4 solution into the waste container.
c. Repeat this process two more times.
5. Make sure the stopcock on the buret is in the "off" position and then use a funnel to fill the buret with about 50 mL of the H2SO4 solution (titrant).
6. Drain a small amount of the titrant through the drop counter into the waste beaker to remove any air in the tip of the buret.
7. Practice adjusting the stopcock on the buret so that the titrant goes through the drop counter in distinguishable drops that fall at about 1 to 2 drops per second (Good control of the stopcock is important. Each drop should result in a blink of the LED on the drop counter. If the LED is continuously lit, you have opened the stopcock too far and you will have to start over.).
8. Add the micro stir bar to the end of the conductivity sensor
9. Add additional 0.02000 M H2SO4 to the buret so the solution is above the zero mark. Allow some of the H2SO4 solution to drip into the waste container until the bottom of the meniscus is lined up with or just below the zero mark and record the initial reading in Table 1.
10. Remove the waste container
11. Use the volumetric pipet to transfer 50.00 mL of the Ba(OH)2 solution with the unknown concentration into a 100-mL beaker
12. Add enough deionized water to the beaker so the tip of the conductivity sensor is covered with solution.
13. Tap the sensor a few times to make sure any trapped air is expelled from the sensor.
14. Turn on the magnetic stirrer at a slow and steady rate.
15. Connect the drop counter to the data collection system.
16. Display the Conductivity on the y-axis of a graph and Drop Count on the x-axis.
Collect Data:
1. Clean the lens of the drop counter inside the opening the drops go through with water and a cotton swab or tissue.
2. Start recording data.
3. Adjust the scale of the graph.
4. Turn the buret stopcock carefully, allowing the titrant to drip slowly (1 to 2 drops per second) into the solution.
5. Continue data collection until the curve passes its minimum point by about 3 mL.
6. Stop recording data.
7. In Table 1, record the final drop count and the final reading of the titrant in the buret to a precision of 0.01 mL.
8. Calculate the volume of titrant (final reading minus initial reading) and record this value in Table 1.
9. Calibrate the drop counter.
10. On the graph, set the horizontal axis to the calculated volume.
11. Print the graph.
12. Find the volume of H2SO4 solution (to a precision of 0.01 mL) used to reach the equivalence point. In Table 2, record the volume (The lowest point of the curve represents the volume of the H2SO4 solution that was required to reach the equivalence point).
13. Refill the buret above the zero mark with H2SO4 solution:
a. Fill the buret above the zero mark and allow some of the H2SO4 solution to drip into a waste container until the top of the meniscus is lined up with the zero mark or just below.
b. Record the starting point in Table 1.
14. Rinse the conductivity sensor top with deionized water.
15. Remove the beaker and dispose of its contents according to the teacher's instructions.
16. Rinse the beaker with distilled water.
17. Begin the second titration of Ba(OH)2 as follows:
a. Use the volumetric pipet to transer 50.00 mL of the Ba(OH)2 solution with the unknown concentration into a 100-mL beaker.
b. Add enough deionized water to the beaker so the tip of the conductivity sensor is covered with solution.
c. Tap the sensor a few times to make sure any trapped air is expelled from the sensor.
d. Turn on the magnetic stirrer at a slow and steady rate.
e. Display the Conductivity on the y-axis of a graph and Drop Count on the x-axis.
f. Repeat the steps following the Collect Data subheading to complete the titration.
18. Save your experiment and clean up according to your teacher's instructions.