Activity 1: What Dissolves and
What Does Not: Establishing Some “Rules”In this laboratory activity you will work with an assortment of solutions of ionic substances, divided into five sets. Your teacher will assign specific sets of solutions for your work. You will compile your data with that of classmates to generate some ‘rules’ regarding solubilities of certain ionic compounds. Using very small quantities, you will mix all possible combinations of solutions in each set and observe any\par reactions that occur.
When you mix certain solutions, you will find that some combinations produce\par precipitates. By comparing data with other students, you should find distinctive patterns developing as certain ions react with each other. From such class data, some generalizations regarding the solubilities of ionic compounds can be drawn. This activity will give you experience in (a) developing laboratory skills, (b) making and recording observations, (c) drawing conclusions and making generalizations from data, and (d) working as part of a team.
Wear protective goggles throughout the laboratory activity.
Although none of the solutions are toxic, place all waste solutions in a properly labeled container. Do not discard the waste in the sink.
Prepare five grid sheets like the following onesolutions in each set.). (The numbers refer to numbered solutions in each set)
Select a set of solutions for the laboratory activity. (Your teacher may select one for you.) Indicate the number of the solution set on the sheet. For each solution in the set, identify the ions present in the solution and record them on the sheet. For example, the sheet for Solution Set No. 1 would look like the one shown. Prepare two sheets for each set of solutions.
Place an acetate sheet, or a small glass plate, over one of the sheets. (Your teacher may prefer that you use cell well plates.)
Carefully add one drop of each solution, where it is indicated on the grid. When you have finished, you will have two drops of solution in each square, and you will have mixed all possible combinations of solutions in the set.
Note any precipitates that form, and record their colors on the second grid sheet that you prepared. Write a net ionic equation for each reaction that produced a precipitate.
Carefully rinse the acetate sheet, or glass plate, with a small amount of water\par into the waste container provided by your teacher. Wash your hands.
Repeat the procedure for the other solution sets assigned to you.
Thoroughly wash your hands before leaving the laboratory.
Compile your data with that of your classmates on the large data table on the chalkboard.
Observe the patterns in precipitation. What conclusions can you draw regarding the solubility of various combinations of ions in solution?
Which of the following pairs of ions should produce a precipitate in water solution?
a. Ag+ + NO3- d. Al3+ + Na+ b. Mg2+ + OH- e. Ag+ + CO32- c. K+ + SO42- f. NH4+ + Cl-
(page 4 & 5)
