Family of Elements

Families of Elements Within families of elements (groups) there are general trends in physical and chemical properties Alkali metals, alkaline earth metals, and halides will be observed in this lab Identification of these elements will be done by their chemical reactions

Flame Tests Flame colors are specific to each element However, flame tests can be misleading Contamination can lead to inaccurate results Sodium as an impurity will give a weak yellow flame, sodium in the sample will produce a strong yellow flame

A. Analysis of Known Solutions 1. Flame tests of known solutions Place 6 test tubes in a test tube rack Add 10 drops of barium, calcium, lithium, potassium, sodium, and strontium to 6 different test tubes Obtain a flame-test wire and remove contamination by placing the wire loop at the tip of the burner flame Continue until there is no longer any color produced in the flame If wire continues to produce a colored flame, dip in dilute HCl (aq) and heat the wire to read hot Dip clean wire into the test tube containing the barium solution Place loop at the tip of the flame Record observation Clean wire and repeat the flame test for the other 5 solutions

A. Analysis of Known Solutions 2. Reactions of Known Solutions Add a few drops of ammonium carbonate solution in each test tube that was used for the flame test If precipitate forms, record ppt in data table If no reaction, record NR Clean test tubes and rinse with DI water Put 10 drops of Ba, Ca, Li, K, Na, Sr into separate test tubes Add a few drops of ammonium phosphate solution in each test tube Record observations

A. Analysis of Known Solutions 2. Reactions of Known Solutions (cont’d) Clean test tubes and put 10 drops of Ba, Ca, Li, K, Na, Sr into separate test tubes Add a few drops of ammonium sulfate solution in each test tube Record observations

A. Analysis of Known Solutions 3. Halide tests of known solutions Place 3 test tubes in a test tube rack Add 10 drops of Br, Cl, and I solution in separate test tubes Add 10 drops of hexane, 1 drop of nitric acid and a few drops of Cl water to each test tube Shake each test tube and observe the color of the upper hexane layer DISPOSE OF HEXANE LAYER IN WASTE CONTAINER PROVIDED

B. Analysis of an Unknown Solution 1. Flame Test Record the unknown number of solution Perform a flame test on solution Record observations

B. Analysis of an Unknown Solution 2. Solution Reactions Put 10 drops of unknown solution into 3 test tubes Add a few drops of Ammonium carbonate to the first test tube Ammonium phosphate to the second test tube Ammonium sulfate to the third test tube Record your observations

B. Analysis of an Unknown Solution 3. Halide Test Put 10 drops of unknown solution into a test tube Add 10 drops of hexane, 1 drop of nitric acid, and a few drops of chlorine water Shake test tube Record the color of the upper hexane layer

Notes Note that problem #10 is not optional Bunsen burners: If you have long hair you must have it pulled back (pony tail) No long dangly sleeves, coats, jewelry