experiment 22 pre laboratory assignment

Experiment #22 Pre-Lab Assignment

1. A saturated solution of lead (II) iodide, PbI2, has an iodide concentration of 3.0 x 10-3 mol/L (see photo).
   1. What is the molar solubility of PbI2?

0.0015 M

• Determine the solubility constant, Ksp, for lead (II) iodide.

Ksp=( x ) (2 x )2=( x ) (4 x²)=4 x³

Ksp=4 (0.001 5³)=1.4 ×10⁻⁸

• Does the molar solubility of lead (II) iodide increase, decrease, or remain unchanged with the addition of potassium iodide to the solution? Explain.

The molar solubility of lead (II) iodide will decrease and shift to the left, because extra products will be added. Thus, the equation will compensate for this added amount of products.

• Experimental Procedure, Part A.4. What is the purpose of rinsing the pipette twice with aliquots of the saturated Ca(OH)2 solution?

The purpose of this technique is to ensure that no contamination of the solution would occur. This is true because the same solution that is being used to rinse the pipette is the one that will be utilized in this part of the experiment.

• Experimental Procedure, Part A.4.
  • What is the indicator used to detect the endpoint in the titration for this experiment? The indicator used to detect the endpoint in the titration of the experiment is the methyl orange endpoint.
  • What is the expected color change at the endpoint in this experiment?

The expected color change in this experiment is to go from yellow to a faint, red- orange.