I. Prepare a series of diluted calcium nitrate solutions 1. Arrange a spot well plate in front of you so that you designate, from left to right, 12 wells to be used in the procedure (probably in a 5,5,2 arrangement). 2. Put 5 drops of 0.10M calcium nitrate in well #1 using the BROWN disposable pipette. 3. Place 5 drops of deionized water in each of the wells #2 through #12. 4. Add 5 drops of 0.10M calcium nitrate to well #2 using the BROWN disposable pipette. 5. Use an empty uncolored unlabeled disposable pipette to mix the solution thoroughly by drawing the solution into the pipette and then squirting it back several times. (The solution in this well is now 0.050M Ca2+). 6. Use an empty uncolored unlabeled disposable pipette to remove the solution from well #2 and put 5 drops of this solution into well #3. Put the remaining solution back into well #2. 7. Mix the solution in well #3 as done previously. 8. Continue this serial dilution procedure, adding 5 drops of the previous solution to the 5 drops of water in each well down the rows until you fill the last one, #12. 9. Mix the solution in well #12 well, and discard 5 drops. 10. Calculate the Ca2+ concentration in each well, and verify that the concentration in cell #12 is 4.9x10-5M. II. Combine with sodium hydroxide 1. Place 5 drops of 0.10M NaOH into each of the wells #1 through #12 using the BLUE disposable pipette. (Note: When the sodium hydroxide is added to each well, the initial concentrations of the reactants are halved, as each solution dilutes the other.) 2. Mix thoroughly with an empty uncolored unlabeled disposable pipette. 3. Verify that the Ca2+ concentration in cell #12 is now 2.4x10-5M III. Observe the precipitates and calculate Ksp  Allow three or four minutes for the precipitates to form. Observe the patter of precipitation. At one point the concentration of both ions becomes too low to have any precipitation form. We will assume that the first well with no precipitate represents a saturated solution.  Calculate the concentration of Ca2+ ions and OH- ions in this well.  Using these concentrations, determine the Ksp of calcium hydroxide. IV. Check using a dilution of sodium hydroxide To check your results, repeat the procedure but use a serial dilution of the NaOH as follows. 1. Arrange a spot well plate in front of you so that you designate, from left to right, 12 wells to be used in the procedure (probably in a 5,5,2 arrangement). 2. Put 5 drops of 0.10M NaOH in well #1 using the BLUE disposable pipette. 3. Place 5 drops of deionized water in each of the wells #2 through #12. 4. Add 5 drops of 0.10M NaOH to well #2 using the Blue disposable pipette. 5. Use an empty uncolored unlabeled disposable pipette to mix the solution thoroughly by drawing the solution into the pipette and then squirting it back several times. (The solution in this well is now 0.050M OH-). 6. Use an empty uncolored unlabeled disposable pipette to remove the solution from well #2 and put 5 drops of this solution into well #3. Put the remaining solution back into well #2. 7. Mix the solution in well #3 as done previously. 8. Continue this serial dilution procedure, adding 5 drops of the previous solution to the 5 drops of water in each well down the rows until you fill the last one, #12. 9. Mix the solution in well #12 well, and discard 5 drops. 10. Add 5 drops of 0.10M calcium nitrate to each of the wells, and mix with an empty uncolored unlabeled disposable pipette. 11. Again, determine the well where there is no precipitate, and again, calculate the value of Ksp for calcium hydroxide. Procedure 1 [Ca2+] After mixing [OH-] After mixing observations [OH-] After mixing observations Well 1 Well 2 Well 3 Well 4 Well 5 Well 6 Well 7 Well 8 Well 9 Well 10 Well 11 Well 12 Ksp calculation: Procedure 2 [Ca2+] After mixing Well 1 Well 2 Well 3 Well 4 Well 5 Well 6 Well 7 Well 8 Well 9 Well 10 Well 11 Well 12 Ksp calculation: V. Consider the following questions. Be complete. 1. How did the values obtained in procedure 1 and 2 compare to each other? 2. Do you think that this method will give values that are too low or too high? Why? 3. What would make the method more accurate? 4. Would your results be better if you averaged the concentrations of the last well where precipitation occurred with the first well where there is no precipitation? Is there justification for doing this? Try it!