Determining Ksp Lab

Purpose

(Put in your lab book)

Determine the solubility product constant of a lead iodide.

Background Questions

(Answer in your lab book)

1. What formula is used when a solution is diluted to determine the new concentration of the solution?

2. What is a solution called if you have not added the maximum amount of solute to the solution?

3. What is a solution called when you have added the maximum amount of solute to the solution?

4. The Ksp formula can only be used when you are at equilibrium. On the computer simulation, how did you know when you reached equilibrium?

5. What happens when you go past the equilibrium point (when you add more than the maximum amount of solute dissolved in the solution)?

6. In lab today, you will be adding lead ions and iodide ions together. In each trial you will increase the concentration of each of the ions to try and find the equilibrium point. How will you know when you are below the maximum amount of lead iodide dissolved in the water?

7. In lab, how will you know when you are above the maximum amount of lead iodide dissolved in the water?

Procedure

(Summarize in lab book)

1. Using a 10 mL graduated cylinder, measure 2.5 mL of 0.010 M lead ions and add it to a clean dry test tube. Add 45.0 mL of water and swirl the test tube. Finally add 2.5 mL of 0.020 M iodide ions. Swirl the test tube and allow to sit while you prepare the other solutions. YOU MUST ADD THE WATER BEFORE YOU ADD THE IODIDE.

2. Prepare four more samples. Each one has a higher concentration of lead and iodide ions. Repeat steps 1 through 3 using the volumes indicated below. Keep the total volume the same every time and you must add the iodide ions last.

Data

(Complete in lab book)

Calculations

(Complete in lab book)

1. Each of the ions are diluted when you pour the water and other solution together. Calculate the new concentration for the lead ion and iodide ion for the ONE solution that is at equilibrium. Show formulas and work clearly in your lab book.

2. Write the equilibrium for lead iodide.

3. Write the solubility product formula (Ksp) for lead iodide.

4. Use your concentrations to determine the Ksp for lead iodide.