LAB 23B Ksp of SILVER ACETATE

LAB 23B Ksp of SILVER ACETATE

BACKGROUND:

You now know something of solubility equilibrium; the rate at which ions are leaving the solid is equal to the rate at which they are re-crystallizing. The balanced equilibrium equation for silver acetate is:

AgCH3COO(s) <===> Ag+(aq) + CH3COO-(aq)

You must now write the equilibrium expression for this reaction. Remember that since pure silver acetate was dissolved you know the concentration of the silver ion must equal the concentration of the acetate ion. Therefore, if you can determine, experimentally, the concentration of one of the ions in solution you will know the concentration of the other and you can calculate the solubility product.

In this lab you will determine the concentration of the silver ions by precipitating them with copper; you have already done this reaction in lab S-3. It would be wise for you to recall the reacting ration between these two reactants.

PROCEDURE:

1. Measure 100.0 ml of saturated silver acetate solution and place it in a clean dry beaker.

2. Obtain a piece of heavy gauge copper wire from the cart. Clean the surface of the wire using emery cloth and mass the copper before placing it into the solution. Record the mass in your data table. Leave the setup stand overnight.

NEXT DAY

3. Shake the crystals free from the wire. I wonder what’s the identity of the crystals? You may scrape any remaining crystals off the wire using your plastic spoon.

4. Wash the copper wire in tap water and then dip it in acetone, found at the front desk. This would allow the copper wire to dry quickly since acetone has a very high vapor pressure. This results from the fact that acetone molecules have very weak IMF’s because they are non-polar. Remember???

5. Mass the copper wire and record the weight in your data table.

6. Decant the solution off the crystals. I wonder what it is made of? Is it safe to pour down the drain?

7. Rinse the crystals with distilled water and place them into the container at the front desk. Why don’t we have to weigh them? Isn’t stoichiometry and the law of conservation of mass wonderful!!!!!!

CALCULATIONS AND RESULTS:

1. Calculate the number of moles of solid copper which reacted.

2. Since you know the reacting ratio between Ag+ and Cu(s) from lab S-3, or use pgs 252-253 in your textbook, you can now determine how many moles of Ag+ were present in the 100.0 ml of solution. Since you know moles and volume please determine the molarity of Ag+ in the saturated solution.

3. What is the concentration of the acetate ions in the saturated solution?

4. Calculate the experimental value of Ksp for silver acetate at room temperature.

5. If 100 ml of .02 M AgNO3 and 100 ml of

.02 M NaCH3COO (strong electrolyte) were mixed, would a ppt of silver acetate form? Use your experimental value Ksp as the accepted value.

6. If NaCH3COO(s) (strong electrolyte) were added to a saturated solution of silver acetate which is in equilibrium with AgCH3COO(s). What would happen to the equilibrium concentrations of all the species?

7. Calculate the [Ag+] if the [CH3COO-] in the solution in question 6 is 1.0 M. I really like this question!!!!