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CChheemmiissttrryy II

Name ______

Purpose: To determine if various ionic compounds obey the solubility rules.

Background: Ionic compounds can be either soluble or insoluble in water, depending on the nature of the intermolecular interactions between the water molecules and the ions that comprise the ionic compound. Shown in Table 1 are the solubility rules that generally apply.

Table 1. Solubility Guidelines for ionic compounds in aqueous solution

Ions that form Ions that form soluble compounds Exceptions insoluble Exceptions compounds + 2- Group 1 ions (Na , Carbonate (CO3 ) Group 1 ions and K+, etc.) ammonium ion 2- Ammonium ion Chromate (CrO4 ) Group 1 ions and + (NH4 ) ammonium ion - 3- Nitrate (NO3 ) Phosphate (PO4 ) Group 1 ions and ammonium ion - - + 2+ 2+ 2- Halides (Cl , Br and Ag , Pb or Hg2 Sulfide (S ) Group 1 ions and I-) ammonium ion 2- + 2+ 2+ 2+ - Sulfates (SO4 ) Ag , Sr , Ba , Pb Hydroxides (OH ) Group 1 ions and and oxides (O2-) ammonium ion

The solubility rules fall into two general types: (1) Ions that generally form soluble compounds, with some exceptions; and (2) Ions that generally form insoluble compounds, with some exceptions. In this experiment you will be given a variety of solid ionic compounds and you will try to dissolve these compounds in water to determine if they are consistent with the solubility rules.

Materials: Beakers, a scopula, deionized water, and at least ten different ionic compounds, containing ions from Table 1.

Procedure: Record the Names and formulas of the available ionic compounds in Table 2. Using Table 1, predict the solubilities of these compounds in aqueous solution.

Using the scopula, place a small amount of one of the solid ionic compounds in a beaker. Add approximately 30-40 mL of deionized water to the beaker. Stir the mixture with the scoupula and try to get the solid to dissolve. Record any observations concerning the compounds solubility in Table 2, including the resulting color of the solution. If the solid did not completely dissolve to form a homogeneous solution, note that the compound appeared to be insoluble.

Name ______

Discard the contents of the beaker, clean the beaker with deionized water and repeat the process for each of the ionic compounds.

Data and Analysis Record the appropriate information in Table 2 concerning the solubility of the ionic compounds in water. Note if there were any discrepancies between your predicted solubilities and the experimentally observed results. Consult your teacher if necessary.

Table 2. Solubility data for ionic compounds.

Compound Name Formula Predicted Observations Solubility

1. For the colored ionic compounds, which ion caused the color? What part of the periodic Table was this ion from?

2. What polyatomic ions always form soluble compounds?

3. What monatomic anions form insoluble compounds?