Lab 7:Determining the Solubility Product Constant
(Ksp)
Purpose:
To determine the solubility product constant for calcium
hydroxide.
Pre lab:
1. Write the balanced equation for the dissociation (dissolving in water) of
calcium hydroxide.
2. Write the solubility product expression for the above reaction.
Procedure:
1. Fill a transfer pipet with saturated calcium hydroxide solution and add 40
drops of the solution to each of three test tubes.
2. To each test tube add 2 drops of phenolphthalein.
3. Fill a different transfer pipet with .10M HCl solution. While carefully
counting the drops add the HCl solution to one of the test tubes until the
pink color disappears. Record the number of drops used
4. Repeat step three with the other two test tubes. Record the number of
drops used.
Test Tube
Drops of Ca(OH)2
Drops of HCl
1
2
3
Questions and Calculations:
1. Calculate the average number of drops of HCl used.
2. Using your pipet and some water to determine how many drops equal a mL.
Then determine the average the average volume in mL of HCl used.
3. Determine the volume in mL of calcium hydroxide used in each test tube.
4. Using the average volume of HCl and the molarity of HCl, determine the
number of moles of HCl used.
5. Write the balanced equation for calcium hydroxide solution reacting with
HCl solution.
6. Using the balanced equation determine the number of moles of calcium
hydroxide needed to react the HCl.
7. Calculate the molarity of the saturated calcium hydroxide solution.
8. Calculate the concentration of each ion in the calcium hydroxide solution.
9. Determine the numerical value of the solubility product constant for
calcium hydroxide.
10. What is your percent error?