Solubility Lab #1 - An Estimation of the Solubility Product of Strontium Chromate
An estimation of the solubility product of a solid can be obtained by mixing solutions of various concentrations of the ions and observing whether a precipitate forms.


Note: All glassware must be rinsed with distilled water and dried before using.  

1.  Add 5.0 mL of 0.2 M K2CrO4 to a test tube containing 5.0 mL of 0.1 M Sr(NO3)2. Shake the contents well and observe. Record your observations. Save the test tube and contents. 
2. To a second test tube, add 5.0 mL of 0.1 M Sr(NO3)2.
3. Measure 2.0 mL of 0.2 M K2CrO4 in a graduated cylinder and fill to the 10 mL mark with distilled water. Pour this solution into a clean, dry beaker to mix it. Add 5.0 mL of this solution to the second test tube. Save the remainder of this solution for the next step. 
4. Pour 20 mL of the remaining solution from 3 into the graduated cylinder and add water to the 10 mL mark. Add 5.0 mL of this solution to the third test tube to which 5.0 mL of 0.1 M Sr(NO3)2 is added. 
5. Continue diluting and mixing in this manner until no precipitate is observed in the test tube. Record the relative amount of precipitation in each test tube. 
6. Always retain the last two (2) diluted solution of potassium chromate (you'll require two beakers for this which you should label appropriately) when no precipitate is observed, dilute the second last solution of K2CrO4 in the following manner. To the remaining 3.0 mL of solution, add 3.0 mL of distilled water. Add 5.0 mL of this to another test tube already containing 5.0 mL of 0.1 M Sr(NO3)2.
7. Complete the following chart including all the required concentrations and observations.
Dilution Number
Initial Conc. of Ions 
in diluted solutions
Concentration upon  mixing
Trial Ksp

[Sr2+] [CrO42-]   [Sr2+   [CrO42-]   [Sr2+] [CrO42-]   ppt?