DRAFT: This module has unpublished changes.

Equipment:

- Data Collection System                          - funnel

- Stainless steel temperature sensor           - dropper

-Ring stand with ring                                - hot plate

- Clamp, utility                                          - clay triangle

- Clamp, buret                                           - 0.5 M Barium chloride (BaCl2)

- Crucible with lid                                     - 0.1 M Silver nitrate (AgNO3)

- Tongs                                                      - 6 M Hydrochloric acid (HCl)

- Beaker, glass, 400-mL                            - Unknown alkali sulfate

- Beaker, glass, 250-mL                            - Filter paper

- Beaker (3), 25-mL                                  - Rubber policeman & stirring rod

- Beaker or flask, 400-mL                         - Watch glass, 100-mm

- Graduated cylinder, 100-mL                   - Distilled water, 100 mL

- Graduated cylinder, 10-mL                     - wash bottle with distilled water

-Buret, 50-mL                                            - Bunsen burner


Safety:

  1. If the HCl comes in contact with skin or eyes, rinse the contacted surface thoroughly with running water.
  2. Barium is a strong poison if ingested. Avoid contact with barium solution. In case of contact with skin, ash the barium off with plenty of water. If ingested, seek medical attention immediately.

Method:

-->Prepare the Solution

  1. Make sure all equipment is clean.
  2. Measure the mass of the unknown sulfate and put it into the 400-mL beaker with 50 mL of distilled water and dissolve it.
  3. Slowly add 5 mL of HCl to the beaker and additional distilled water until there is 250 mL of the solution in the beaker.
  4. Cover the beaker with the 100-mm watch glass.

-->Form the Precipitate

  1. Start a new experiment on the data collection system, set it to monitor live data, and connect the stainless steel temperature sensor to the data collection system.
  2. Use the buret clamp and attach the buret to the ring stand.
  3. Place the beaker with the solution on the hot plate and heat it to 90 oC and put the temperature sensor into the solution making sure it does not touch the beaker
  4. When the solution has reached 90 oC add 25 to 35 mL of BaCL2 solution from the buret into the beaker and then let it settle
  5. After the precipitate has settled, test for completeness by adding a couple drops of BaCL2 . If there is any sign of precipitation, add 5 more milliliters of BaCL2
  6. Cover the beaker with a watch class and continue to heat at 90 oC for one hour to allow the precipitate to become coarse

-->Collect the Precipitate

  1. Fold a piece of filter paper in half, then in half again, form a cone, and put it into the funnel.
  2. Support the funnel in the ring mounted on a ring stand over a beaker to hold all of the supernatant.

-->Collect Data

  1. In the 250-mL beaker heat 100 mL of distilled water to 80 oC for rinsing the precipitate.
  2. Pour the mixture with the precipitate through the funnel with the filter paper.
  3. Wash the material in the funnel with three 5-mL portions of the hot, distilled water and collect the washes separately in the 25-mL beakers.
  4. Add two drops of the AgNO3 solution to the last wash and if any cloudy white precipitate is observed, the precipitate still contains chloride ions and must be washed with hot distilled into a rinsed beaker until it is no longer cloudy.
  5. Clean and dry a crucible and lid and place it on the clay triangle over the Bunsen burner.
  6. Heat the crucible and lid for about 15 minutes and then let it cool to room temperature.
  7. Obtain the mass of the “fired” crucible and lid and repeat the heating/cooling process until two readings for the mass are within 10 mg of each other.
  8. Remove the filter paper with the precipitate and fold it and put it in the crucible and heat it on a wire triangle on a ring stand over a Bunsen burner. Make sure the flame is small enough that the filter paper does not burst into flame.
  9. When all of the carbon residue from the filter paper has been removed, the temperature should be maximized and the crucible should be heated for ten more minutes.

    10. Allow the crucible to cool for a few minutes and then place it into a desicator using crucible            tongs until it’s cooled to room temperature at which point the mass of the crucible, lid, and                  precipitate needs to be obtained.


    11. Repeat the heating/cooling process until two successive mass measurements are within 10             mg of each other.


    12. Clean up all materials and lab area.

DRAFT: This module has unpublished changes.