tmining the K., of Calclum Hydroxide 123 urose: To determine the solubility Eurp
ID: 103477 • Letter: T
Question
tmining the K., of Calclum Hydroxide 123 urose: To determine the solubility Eurpose: To determine the solubility product constant, K g, of solid calcium hydroxide Materials: . spot plate 0.100 M calcium chloride (CaCI,) e 0.100 M sodium hydroxide solution (NaOH) transfer pipettes distilled water Procedure 1. Thoroughly wash and dry your spot plate 2. Label the wells of your spot plate #1-12 3. Using a clean transfer pipette, add 5 drops of distilled water to wells #2-11 4, Using a clean transfer pipette, add 10 drops of calcium chloride solution to well #1 5, Draw the solution from well #1 into a transfer pipette and place 5 drops of the solution into well #2. Return the excess solution in the pipette to well #1 Draw the solution from well #2 into a transfer pipette and place 5 drops of the solution into well #3. Return the excess solution in the pipette to well #2 Repeat this process for each of the remaining wells. For well #12 discard the 5 drops into the sink, with running water With another clean transfer pipette, add 5 drops of sodium hydroxide solution to each of the wells 6, 7, 8. 9. Use the tip of the pipette to mix the solutions well. 10. Examine all of the wells for the presence of a precipitate (allow a few minutes for a precipitate to form)Explanation / Answer
The experiment involves as number of transfer from one spot on a spot well to another. Volume transfers from one spot to another can cause errors, especially if the experimenter doesn’t pay attention to numbering the spots correctly or simply forgets to do the serial dilutions (transferring from one spot to another is in effect a serial dilution).
Another source of error can be contamination. The spot well and the pipettes used must be washed and dried properly. Washing properly is essential to make sure that no undesired materials are left in the pipette. Washing with water and then with the test solution is essential to ensure that the pipette is free from all impurities.
Drying the pipette is important to make sure that water is not sticking to the glass of the pipette. Water can cause the solutions to get diluted and the dilute solutions may not have the proper concentrations of the ions to cause a precipitation.
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