Experiment #6
Determination of the solubility product of PbI2
Introduction:
The purpose of this lab is to get familiar with the concept of solubility by determining the concentration of PbI2 and Pb2+ in the slightly acidic solution and to calculate the solubility constant using the equation Ksp=[Pb2+][I-]2 .
Safety:
Safety glasses must be worn at all times. Gloves are recommended in order to avoid the direct contact between skin and the chemicals. Avoid the spill of chemicals during shaking the solution in the test tube. Must dispose liquids with lead in inorganic waste and filter paper in solid waste. The other liquids can be disposed in the drain with a lot of water.
Procedure:
Use the graduate cylinder next to the stock solution, obtain approximately 35ml of 0.012M Pb(NO3)2 in 0.20M KNO3 into a 250ml beaker. Use the graduate cylinder next to the stock solution, obtain approximately 30ml of 0.03M KI in 0.20M KNO3 into a 150ml beaker, and use the graduate cylinder next to the stock solution obtain 10ml 0.20M KNO3 into a 50ml beaker. Label four test tubes as 1,2,3 and 4. Pipet 5ml of 0.012M Pb(NO3)2 into each test tube, and pipet 2ml of 0.03m KI in KNO3 and 3ml of 0.2M KNO3 into test tube 1, pipet 3ml of the same solution and 2ml of 0.2M KNO3 into test tube 2, pipet 4ml of the same solution and 1ml of 0.2M KNO3 into test tube 3, and pipet 5ml of the same solution into test tube 4. Stopper each test tube using parafilm and shaker the test tube thoroughly for few minutes. Obtain a fifth test tube and pipet 10ml of 0.012M Pb(NO3)2 in KNO3 and 10ml of 0.03M KI in KNO3 and shake the mixture solution and wait for the precipitate to settle. Use stirring rod to decant the solution. Add approximately 3ml of 0.2M KNO3 into the fifth test tube and shake it and decant the solution again, discard the liquid. Add 0.2M KNO3 into the fifth test tube until the test