Name That Salt. The six salts used in this experiment are:

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1 Name That Salt Learning Objectives: In this experiment there are six unidentified salts labelled Salt 1 through Salt 6. Each team will be given one of these salts and their job is to determine the identity of their salts. The six salts used in this experiment are: sodium chloride (NaCl) sodium sulfate (Na 2 ) potassium chloride (KCl) potassium sulfate (K 2 ) lithium chloride (LiCl) lithium sulfate (Li 2 ) Background: The six possible unknowns we will investigate are all inorganic compounds These inorganic compounds are ionic salts made up of cations and anions Sodium, potassium, and lithium are cations that have a positive charge and are the metallic portion of the salt Chloride and sulfate are anions that have a negative charge and are the acidic portion of the salt Experimental Background: Two tests are performed to confirm the identity of each salt. The first test is a flame test to determine the cation. Following the experimental procedure below, the presence of Sodium will be indicated by a yellow colored flame, Potassium by a lilac colored flame and lithium by a magenta colored flame. The second test, for the anion (either chloride or sulfate) will be done using a precipitation test. Silver nitrate will form a white precipitate (silver chloride) if chloride is present and no precipitate (clear solution) if sulfate anion is present. Equipment and Materials: Test tubes and rack Spatula Permanent marker Platinum or nickel chromium wire loops for flame test 0.1N HCl Deionized water 0.1N Silver nitrate 2 x 10 ml graduated cylinders, one marked with red tape for the 0.1N HCl and one marked with blue tape for the deionized water Waste buckets for liquid and used test tubes Ultrasonic bath Vortex mixer Glass mortar and pestles 3 unknown salt shakers, containing either NaCl, KCl, or sugar Salted corn chips and unsalted corn chips

2 Set up: Lab Station Set up and Reagent prep There will be 6 work stations, and each work station will have a different unknown salt labeled from 1 to 6. The instructor has a master indicating which unknown is which salt. Each work station will have a test tube rack filled with test tubes, a permanent marker, a spatula, DI water, 0.1N HCl, and 0.1N silver nitrate. The flame test will be performed under the fume hood using one Bunsen burner under the supervision of an instructor. Wires should be cleaned with 0.1 N HCl before class. A copper sulfate solution (from the electroplating experiment) can be used as a demonstration flame test (green color flame) using a dedicated wire. The ultrasonic bath and vortex mixer will be on a separate lab bench. The unknown salt shaker and corn chip experiments will be staged on a separate lab bench Experimental Procedure: Cation Determination 1. Take the permanent marker and label a test tube with the number of your salt and the words Cation Test. 2. Using the spatula, remove a small portion of your salt and place it in the tube. 3. Add 4 ml of 0.1N hydrochloride acid (HCl) solution. 4. Sonicate or vortex to dissolve. 5. Did the salt dissolve easily? 6. Dip the end of the innoculating loop into the solution and hold it in the flame. A color will appear. 7. Compare the color to the table. On your worksheet, record the color and which metal: sodium (Na + ), potassium (K + ), or lithium (Li + ) it represents.. Anion Determination 1. Take the permanent marker and label a second test tube with the number of your salt and the words Anion Test. 2. Using the spatula, remove a small portion of your salt and place it in a second test tube. 3. Add 5 ml of deionized water. 4. Vortex to dissolve. 5. Place 1-2 drops of 0.1N silver nitrate (AgNO 3 ) solution into the test tube. 6. Did a precipitate form with the addition of the silver nitrate solution? Record observation on worksheet 7. Record which anion is present (If the chloride anion (Cl - ) is present a thick white precipitate will form. If the sulfate anion ( 2- ) is present, there will be no visible change to the solution in the test tube.)

3 Which Salt do you have? Cations- Flame Test Sodium (Na + ) Orange-yellow Potassium (K + ) Lilac Lithium (Li + ) Magenta Anions- Silver Nitrate Reaction Chloride (Cl - ) White precipitate 2- Sulfate ( ) Clear solution Unknown Salt Flame Testing (Color) Precipitation Testing NaCl Orange-Yellow White precipitate KCl Lilac White precipitate LiCl Magenta White precipitate Na 2 Orange-Yellow Clear solution K 2 Lilac Clear solution Li 2 Magenta Clear solution The Conclusion: Each team will record the identity of their salt on the score sheet. Once all teams have recorded their results, the actual identity of each salt will be revealed.

4 Answer Key: Salt 1 = Potassium Chloride (KCL) Salt 4 = Sodium Chloride (NaCl) Salt 2 = Potassium Sulfate (K 2 ) Salt 5 = Lithium Chloride ( LiCl) Salt 3 = Lithium Sulfate (LiSO4) Salt 6 = Sodium Sulfate (Na 2 ) Salt Shakers: = Potassium X = Sodium = Sugar Corn Chips 1 = Salt 2 = No Salt

5 Instructor Notes: Go over the entire experiment with the students and explain the 2 tests that will be performed, demonstrate how the ultrasonic bath and vortex mixer works, and demonstrate the flame test using the copper sulfate solution. Then have the students do the experiment with the instructor and assistants observing. The students perform the flame test themselves and you can show the different flame colors to all the students so they can see for themselves. Consistency is necessary for the flame test. Use the same part of the flame and same technique to avoid false results. The NiCr wire will burn yellow but the sodium yellow is a flash that occurs when you first put the wire in the flame. Sometimes the lilac color from potassium can be hard to see at first but keep repeating and you will see it. Also, sugar (from the unknown salt shaker exp. ) burns yellow but there is a difference between this color and Na and you can smell the sugar burning which you should point out to the students. After the students determine their unknown salt, there will be extra time to perform 2 additional experiments which the students can do based on what they have learned. In the first additional experiment, explain to the students that in a certain nursing home, the residents are on a low sodium diet (because of blood pressure, heart problems) and the salt shakers are filled with potassium chloride, a salt substitute. However some staff member at the nursing home screwed up and accidentally put sodium chloride in some of the salt shakers and sugar in others. The students need to determine which salt shaker contains NaCl, KCl, and sugar. Ask them how they can determine this. Suggestions such as taste, observation, etc. are good but they should use the lab technique they just learned ie. the flame test. Have each team pick one salt shaker (identified by dot, square or star) and use the same lab procedure as they did for the unknown salt. If there are more than 3 teams, the additional teams can repeat a salt shaker or move on to the corn chip experiment. In the corn chip experiment, explain to the students that at this same nursing home where the residents are on a low sodium diet someone mixed up batches of salt free corn chips with salted corn chips. Again, the students must determine which is which by the flame test. In this experiment the students pick a batch of corn chips, grind up a chip in a glass mortar and pestle (demonstrate how to do this) transfer the ground corn chip to a test tube and use the flame test procedure for work up. However explain that the corn chip will not dissolve but that s OK since we only need to dissolve the NaCl if present. Another good demonstration for the students if time permits is to show why it is important to use deionized water and not tap water for the precipitation experiment. Ask one student to fill up a test tube half way with tap water and another student to do the same with deionized water. Then add a few drops of silver nitrate to each and see what happens. The tap water should show a precipitate which would be a false positive for sodium, wheras the deionized water should be clear. Talk to the students about how the fireworks industry uses inorganic salts such as used in this experiment to produce the colors we see in fireworks displays. You can also talk to the more advanced classes about the physics involved in exciting molecules and the light energy and color emitted as they return to their ground state. You will know when their eyes gloss over that it is time to stop this discussion.