Question

A Solubility Product Constant Introduction: Many substances are very soluble in water. However, in this experiment you will be concerned with substances that are insoluble or only slightly soluble. Dynamic equilibrium is established when an excess of a slightly soluble substance is placed in water. The rate of dissolution of the ions from the solid equals the rate of precipitation of the ions from the solution. Lead II Chloride is an example of a sparingly soluble salt. The equation for the solution reaction of PbCl, is: PbCl2 → Pb) + 2 CIQ) The solubility product expression for this reaction is: Ksp [Pb*)(CM12 This equation means that for any system containing a solid PbCl2 in equilibrium with its dissociated ions, the product of the magnesium ion concentration, [Pb 2), multiplied by the carbonate ion concentration, [CI], will be a constant, Ksp. The Ksp is constant at a given temperature. It is usually reported at 25°C. In this experiment, you will find Ksp of PbCl2. Beginning with a saturated solution of the salt, you will precipitate Pb 2 ions as insoluble lead II chromate, PbCrO4. From the amount of lead chromate obtained, you will determine the concentration of Pb+ ions in the saturated solution. Once you have established the concentration of lead ions, you can calculate the concentration of chloride ions and compute the Ksp for PbCl2. Learning Outcomes: 1. You will determine the concentration of Pb+2 ions in a saturated solution of PbCl.. 2. You will calculate the Ksp for PbCl2. Materials: glass funnel 2-50 mL beakers glass stirring rod 25.0 mL volumetric pipet 5.0 mL volumetric pipet pipetters Ring stand distilled water Wire gauze balance Bunsen burner or hot plate drying oven Wash bottle filter paper Solutions: Saturated lead II chloride 0.5 M potassium chromate

#5 Write the solubility product expression for PbCl2. Using the concentration for the Pb+2 and Cl- ions, solve for your experimental Ksp.

#6 Using your book, find the theoretical Ksp for PbCl2 to determine your percent error