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AP Chemistry Background The solubility product constant, Ksp, is a particular type of equilibrium constant. The equilibrium is formed when an ionic solid dissolves in water to form a saturated solution. The equilibrium exists between the aqueous ions and the undissolved solid. A saturated solution contains the maximum concentration of ions of the substance that can dissolve at the solutions temperature. A knowledge of the Ksp of a salt is useful, since it allows us to determine the concentration of ions of the compound in a saturated solution. This allows us to control a solution so that precipitation of a compound will not occur, or to find the concentration needed to cause a precipitate to form. The solubility product which will be determined by this experiment is that of the strong base, calcium hydroxide, Ca(OH)2. Materials and Equipment Calcium nitrate, Ca(NO3)2, 0.10 M Sodium hydroxide, NaOH, 0.10 M (2) 96-well micro-wellplates 50-mL beaker Small dropper bottles for Ca(NO3)2, NaOH, and H2O (2) disposable pipets for mixing Note Hold the droppers vertically when dispensing the drops. Discard the first drop as it may contain an air bubble. Procedure Part A Ca(NO3)2 varies, NaOH held constant Arrange a micro-wellplate so that you have 12 wells up and down. Put 5 drops of 0.10 M Ca(NO3)2 in well 1 in the first row. Place 5 drops of water in each of the wells 2 though 12 in the first row. Next add 5 drops of 0.10 M Ca(NO3)2 to well 2. Use an empty pipet to mix the solution thoroughly by drawing the solution into the pipet and then squirting it back several times. (Calculation hint the solution in this well, 2, is now 0.050 M in Ca2 ion.) Use your empty pipet to remove the solution from well 2 and put 5 drops of this solution into well 3. Put the remaining solution back in well 2. Mix the solution in well 3 as before. Continue this serial dilution procedure, adding 5 drops of the previous solution to the 5 drops of water in each well down the row until