Precipitation Reaction and Solubility Rules
Introduction: This lab is intended to let you observe the solubility rules for ionic substances in ‘action’. You will conduct numerous reactions, determine the solubility of the products, analyze the patterns and formulate your own solubility rules based upon your observations.
Background: Ionic salts are compounds composed of two parts-cations (positively-charged ions) and anions (negatively charged ions). When ionic salts are dissolved in water, the salt crystal dissociates or separates into the corresponding cations and anions.
K+(aq) + 2I-(aq) + Pb2+(aq) + NO3- " PbI2(s) + K+(aq) + NO3-(aq)
Concepts: Precipitation reactions Solubility rules
Materials
Chemicals: Part I
Silver nitrate, AgNO3, 0.1M
Barium chloride, BaCl2, 0.1M
Sodium carbonate, Na2CO3, 0.1M
Ammonium sulfate, (NH4)2SO4, 0.1M
Lead nitrate, Pb(NO3)2, 0.1M
Calcium nitrate, Ca(NO3)2, 0.1M
Potassium phosphate, K3PO4, 0.1M
Part II
Iron (III) chloride, FeCl3, 0.1M
Sodium hydroxide, NaOH, 0.1M
Lead nitrate, Pb(NO3)2, 0.1M
Sodium sulfate solution, Na2SO4, 0.1M
Magnesium bromide, MgBr2, 0.1M Sodium chromate, Na2CrO4, 0.1M
Potassium carbonate, K2CO3, 0.1M
Equipment: Plastic dropper bottles containing chemical solutions as listed above Data Tables
Safety Precautions:
Toxic by Ingestion- Barium chloride, lead (II) nitrate, sodium chromate
Toxic, Corrosive, Light-sensitive, Stains skin and clothing -Silver nitrate
Corrosive, Body tissue irritant -Sodium hydroxide
***Wear goggles, chemical-resistant gloves and chemical-resistant aprons.***
Procedure: Part I-Mixing Pairs of solutions/Data Table I
1. Take reagents to your workstation
2. Place a 12-well reaction plate on top of the black table as shown in Data Table 1
3. Using Data Table 1 as a guide, place 1 drop of AgNO3, into well A1. Hold bottles vertically to ensure uniform drops.
4. Add 1 drop AgNO3 to each well down the vertical column 1, wells B1 through F1.
5. Fill each vertical column with 1 drop of each solution as follows:
6. Place 1 drop of BaCl2 into wells B2-F2
7. Place 1 drop of Na2CO3 into well C3-F3
8. Place 1 drop of (NH4)2SO4 into wells D4-F4
9. Place 1 drop of , Pb(NO3)2 into wells E5-F5
10. Place 1 drop of Ca(NO3)2 into well F-6
11. Now add 1 drop of BaCl2 to the solution in A-1.
12. Record your observation immediately. ( Note: if a precipitate is formed, write “PPT” in the correct circle of Data
Table # 1. Record the color of the precipitate. If no precipitate appears to have formed, write “NR” for no reaction in the
correct circle of the data table. Make sure to leave space in the circles to also write the two possible products of the reactions.)

13. Continue the process of mixing solutions by adding 1 drop of each solution listed along the left side of Data Table 1 to the correct well. Record your observations immediately as described in Step 7.
14. Once you have completed using all the wells on the plate for the different reactions, rinse the plate off in the sink, dry and then reuse for the next set of reactions.
Procedure: Part II-Mixing Pairs of solutions/Data Table II
1. Take reagents to your workstation
2. Place a 12-well reaction plate on top of the black table as shown in Data Table 1
3. Using Data Table II as a guide, place 1 drop of FeCl3, into well A1. Hold bottles vertically to ensure uniform drops.
4. Add 1 drop FeCl3 to each well down the vertical column 1, wells B1 through F1.
5. Fill each vertical column with 1 drop of each solution as follows:
6. Place 1 drop of NaOH into wells B2-F2
7. Place 1 drop of MgBr2 into well C3-F3
8. Place 1 drop of K2CO3 into wells D4-F4
9. Place 1 drop of , Pb(NO3)2 into wells E5-F5
10. Place 1 drop of Na2SO4 into well F-6
11. Now add 1 drop of NaOH to the solution in A-1.
12. Record your observation immediately. ( Note: if a precipitate is formed, write “PPT” in the correct circle of Data
Table # 1. Record the color of the precipitate. If no precipitate appears to have formed, write “NR” for no reaction in the
correct circle of the data table. Make sure to leave space in the circles to also write the two possible products of the reactions.)
13. Continue the process of mixing solutions by adding 1 drop of each solution listed along the left side of Data Table 1 to the correct well. Record your observations immediately as described in Step 7.
14. Once you have completed using all the wells on the plate for the different reactions, rinse the plate off in the sink, dry and then reuse for the next set of reactions.
Data Analysis:
Part III-Making a List of Soluble, Insoluble and Unknown Substances
1. Be sure to label each well with the formulas for the two possible double replacement products. This should be done even if there was no reaction (no formation of a precipitate).
2. Use Table 3 to make a list of ALL the substances that you know to be soluble in water. Generate this list by:
3. Writing down each solution that you used in this experiment from the materials list-these are ALL soluble.
4. Look at your observations in the data tables. For each reaction that did not produce a precipitate (NR), four substances are now known to be soluble-the two starting substances and the two possible products.
5. Generate a list of ALL substances that you now know are insoluble . These were the substances that produced a precipitate. If neither one of the new substances appear on the soluble list, then place both substances in the Unknown column. Write the two substances together as a pair. This way, later you will know that if one substance is found to be soluble, the other must be the insoluble one.
6. Organize your lists of soluble and insoluble substances. Cross out any duplicate entries.
7. On a copy of Table 3, categorize and alphabetize columns 1 & 2 by the anion present. Example: Compound is potassium chloride-it will be listed as chloride, potassium. For column 3,(Unknown substances) leave written as their normal salt name. MOST solubility rules are based on the anion.
Part IV-Analyzing the Solubility List and Developing General Solubility Rules
1. Examine the pairs of substances in the UNKNOWN column of Table 3. Look for any substances that can now be definitely determined to be soluble or insoluble. Add them in the correct column in Table 3.
2. Look for any common relationships among the substances in the unknown column and that of the soluble or insoluble substances. The objective at this point is to remove all of the substances from the unknown column and place in either the known or unknown columns USING LOGIC. [For example-are most or all of the nitrate compounds in the same column?] Use the categories in Table 4 to help you make some of the conclusions here.
3. Fill in Table 4 with the solubility of each group, including any exceptions that you have observed.