Competitive Event (individual) – SSC-A3??
Dr. J. D. Foote (Chemistry Department)
Each participant will receive ten test tubes. Each numbered test tube will contain a different inorganic salt dissolved in water or one of the test tubes might contain just water. The problem is to discover which inorganic salt is contained in each tube.
A. Equipment. Each participant will receive ten test tubes filled with various aqueous salt solutions (one might contain only water), a spotting dish, litmus paper, and ten pipets. Should you run out of a solution, you will not be able to obtain more.
B. Procedure. To determine what is in each test tube, two drops of the solution from one test tube should be mixed in a depression of the spotting dish with 2 drops of another solution. Note the reaction and proceed to test as many combinations as are needed to verify the identities of the ten solutions. NOTE: Pipets should not be transferred from one solution to another without rinsing.
C. Interpretation of Results. The following substances may be found in your test tubes: NaBr (sodium bromide), HCl (hydrochloric acid), H2SO4 (sulfuric acid), NaOH (sodium hydroxide), BaCl2 (barium chloride), CuSO4 (copper sulfate), Na2S (sodium sulfide), NH4Cl (ammonium chloride), AgNO3 (silver nitrate), KI (potassium iodide), and H2O (water).
Below is a list of a few of the reactions you might expect.
1. H2O will give no reactions.
2. Acid and CuSO4 turn blue litmus paper pink.
3. Acid and Na2S produce a white precipitate and the odor of rotten eggs.
4. If a base is mixed with NH4Cl, ammonia gas is given off. Ammonia vapor turns
pink litmus paper blue.
5. Any substance that contains halogen (halogens are Cl, Br, or I) will produce
a precipitate, dark gray to white in color, when mixed with AgNO3.
6. CuSO4 produces an orange precipitate when mixed with KI but doesn't produce
a precipitate with NaBr.
7. BaCl2 and KI produces no precipitate; however, when BaCl2, KI, and H2SO4 are
mixed, a white precipitate is formed.
8. Acids turn blue litmus paper pink; bases turn pink litmus paper blue.
The first person to correctly submit, in writing, the identity of all ten test tubes to the judge will be declared the winner. No participant will be permitted to continue work after submitting their list to the judge. If no one has correctly identified all 10 test tubes by the end of the period, then the winner will be the person who identifies the most number of test tubes correctly. NOTE: The students will be permitted to use our "Interpretation of Results" table or their own reaction table during the contest.