Experiment 6 pre-lab
1. Ken McFarland “Determination of a Solubility Product Constant”, CHEM 1130, TA Nastaran Marzijarani, Section 108, Room 1871, Will Brubacher, Thursday 2:00 pm
1. Purpose of Experiment: This experiment is to find the Ksp of Ca(IO3)2 ●xH2O through the
titration of saturated solutions.
2. Procedure:
Materials: Beaker, 250 mL & 400 mL, 10.00 mL pipette, 0.240 M potassium iodate
solution, Erlenmeyer flasks, buret, graduated cylinders, calcium iodate in water, calcium
iodate in KIO3, 0.0500 M sodium thiosulfate solution, 1 M HCl, 1% starch solution
Get 35 mL of HCl, 40 mL of Ca(IO3)2 in water, and about 200 mL of KI solution, and place
them all in clean beakers. Rinse the buret with the sodium thiosulfate solution. Place 50 mL
of KI solution, 10.00 mL of Ca(IO3)2 solution, 10 mL of HCl to a 250 mL Erlenmeyer flask.
Carefully titrate with the sodium thiosulfate until the solution is yellow, and then add 10
drops of the starch indicator, and the solution should turn blue-black. Continue titrating until
the solution is colorless. Do this titration two more times. The readings should agree to
within +/- 0.50 mL. See instructor if they do not.
Obtain about 35 mL of HCl, 40 mL of Ca(IO3)2 in KIO3, and 200 mL of KI in clean beakers.
Refill the buret with sodium thiosulfate. Add 50 mL of KI solution, 10.00 mL of Ca(IO3)2 in
KIO3, and 10 mL of HCl to a clean 250 mL Erlenmeyer flask. Titrate this in the same manner
as the first titration, adding starch when the solution turns yellow, and titrating until clear.
This titration should also be done a total of three times, with similar error to the first.
3. Observations, Results and Data Sheets: See attached data sheet.
4. Questions:
1. Pure water
2. The addition of the KIO3 means that there are already IO3- ions in solution, so the CaIO3
is less soluble.
3. The Ksp for pure water is twice the size of the Ksp for the common ion solution. They
should not be similar, because one of the solutions is pure water, and one already has one
of the two ions in it.
4. Na2IO3 would work as a soluble source of the IO3- ion.
5. Half the data was gathered by another group. A change in temperature between the two
sets of data, even slightly different, could have significantly changed the Ksp value.