The only way to find out whether or not a compound is soluble in water is to test it. Solubility rules are the results of completed investigations. It is productive to have the rules developed so you don’t have to run to the lab every time you need to know whether or not a precipitate will form.

The solubility of an ionic compound in water depends on the ions that make it up. Some ions are more soluble than others. When determining the solubility of a compound, you must consider both the cation and anion.

The following video will guide you through several experiments to determine the solubility of various ions. Copy the chart below into your notes.

  F- Cl- Br- I- OH- SO4-2 CO3-2 S-2 PO4-3
AG+                  
NH4+                  
Mg+2                  
Ca+2                  
Sr+2                  
Ba+2                  
Zn+2                  
Cu+2      
X
          
Al+3                  
Pb+2                  
Fe+3                  

Video segment. Assistance may be required. As you watch the video, note your observations in the table. You will then use your observations to draw conclusions about the solubility of various ions.

Source: Solubility Rules, NCSSMDistanceEd, YouTube

Mouse over the cells to enlarge the print.

Use your observations, to answer the following questions in your notes.

  1. What does it mean if the solution remains clear?

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    If the solution remains clear, that means that no insoluble product is formed.Close Pop Up

  2. What does it mean if the solution gets cloudy or changes colors?

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    If the solution gets cloudy or changes colors, that means that an insoluble product is formed; the compound of those two ions is insoluble in water.Close Pop Up

  3. Is the following statement true or false: Ag+ ions always form insoluble compounds. Fully explain your answer using evidence from the lab data you gathered.

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    The statement is false because Ag+ forms a soluble compound when combined with F- and SO4-2.Close Pop Up

  4. How does the solubility of the NH4+ ion compare with the solubility of the Ag+ ion?

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    The NH4+ ion is more soluble than the Ag+ ion. All of the tested ions formed soluble products with NH4+ ions. However, Ag+ only formed two soluble compounds out of the tested ions.Close Pop Up

  5. What is the only soluble compound formed by the Pb+2 ion?

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    PbCl2Close Pop Up