SCH4U
Name:
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Determination of the Solubility Product Constant for Calcium
Hydroxide
The solution process can be considered as an equilibrium process and as a result, an equilibrium
constant can be assigned. It is given a special designation, Ksp.
In this investigation, you will determine the value of the Ksp for calcium hydroxide. You will be
given a saturated solution of calcium hydroxide with an excess of crystals on the bottom. The
solution will be at room temperature. To calculate the Ksp value, the concentration of hydroxide
ions and calcium ions in the equilibrium solution are needed. The [OH-] will be found by titrating
a sample of the saturated solution with acid of known concentration.
Pre-lab
1. Write an introduction for this lab, as if you were writing a formal lab report. You MUST have
references and they MUST be written in APA format. [
/5]
2. Make a check-list for this lab. Make sure that each term in the check-list has only ONE task.
[
/3]
3. Make a chemical safety table for all the chemicals used in this experiment. Refer to the Esters
lab for an example. [
/2]
4. Find the Ksp value for Ca(OH)2 [
/1]
Materials
Burette
Pipette
Distilled water
Pipette bulb
Erlenmeyer flasks
Saturated calcium hydroxide solution
Methyl orange indicator
0.05 M HCl
Procedure
1. The saturated solution of calcium hydroxide has already been prepared for you. It has been
“equilibrating” for at least six days
2. Prepare a 50 mL burette for titration. Rinse the clean burette and tip with 5 mL portions of
standardized 0.05 M HCl solution and discard the washing. Repeat this procedure again.
3. Fill the burette with HCl and record the initial volume
4. Try to keep the undissolved calcium hydroxide so that it remains on the bottom of the flask.
With minimum disturbance, carefully decant the saturated solution into a second flask. Take
approximately 50 mL of saturated solution
5. Record the temperature of the sample taken
SCH4U
Name:
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6. Rinse the 10 mL pipette with 2 mL of the saturated hydroxide solution and discard. Pipette 10
mL of the saturated hydroxide solution into another clean Erlenmeyer flask. Add two drops of
methyl orange indicator
7. Titrate with the standard 0.05 M hydrochloric acid solution. Record the volume needed to just
turn the yellow colour to a permanent pink.
8. Repeat the process until the numbers are within 0.2 mL
9. All waste is to be discarded in the container provided for this purpose.
Questions
1. Calculate the moles of acid used in the titration [
/3]
2. From a balanced chemical equation for the titration reaction, determine the moles of OH- ion
used in the reaction [
/2]
3. Calculate the concentration of OH- ions and Ca2+ ions in the saturated solution, in mol/L
[
/3]
4. Why does the reactant not appear in the equilibrium law for this equilibrium? [
5. Calculate the value of Ksp for Ca(OH)2 [
/1]
/6]
6. 200 mL of 1.500 M CaI2 was added to 100.0 mL of the saturated Ca(OH)2 solution. Calculate
the equilibrium concentration of the OH- ion [
/4]
Lab Skills
-
All equipment was used properly
All chemicals were used and disposed of properly
The lab area was cleaned properly
The results were accurate
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