VI-1 Chem 2115 Experiment # 6 PERIODIC RELATIONSHIPS

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C. Place a small piece of Mg and Al into separate test tubes. Carefully add 3 mL of 6 M HCl (hydrochloric acid) drop by drop. Observe the reactivity of each metal. Which is the most reactive? Notebook observations: I. Reactivity of Metals: Observations for this section should include color changes, bubbling (gas formation), temperature changes, formation/disappearance of a precipitate, and color when phenolphthalein is added. II. Halogens (Parts II A and IIB will be demonstrated by your instructor) A. Observe and describe the color and physical appearance of bromine in a closed tube when the end of the tube is immersed first in ice water and then in warm water. B. A few crystals of iodine will be placed in a small beaker and heated. The beaker will be covered with a watch glass that has some ice on it. Observe what happens to the iodine in the beaker and the formation of iodine crystals on the watch glass. The violet fumes are gaseous I2 vapor. CAUTION: Iodine is a toxic material; avoid breathing the fumes. C. Place 2 mL of aqueous solutions of Cl2, Br2, and I2 into separate test tubes. Observe the characteristic colors of each of the aqueous solutions. To each tube add 1 mL of hexane. (note which layer is the hexane layer. Is it on top or bottom?) Water and hexane are immiscible (not mutually soluble). Stopper the tube (do not use your fingers) and shake vigorously. Observe the color of each halogen in the hexane layer. Halogens are more soluble in hexane than in water, so the halogen (Cl2, Br2, or I2) will move to the hexane layer. The colors in hexane are characteristic of the halogen and can be used to identify which halogen is present in a sample. Notebook observations: IIA and B. Observations for these sections should include changes in state and colors observed. II C. Prepare a table of observations with three columns (Halogen, color of water layer, and color of hexane layer) and with rows for Cl2, Br2 and I2 Since water is denser than hexane, the aqueous layer is on the bottom of the test tube. <strong>VI</strong>-4
III. Halide Salts A. Observe the appearance of three halide salts - KCl, KBr, and KI - as solids and in solution (if any). Put a few crystals of each one into separate test tubes, add water, and shake to see if they dissolve. Put a few crystals of each one into separate test tubes, add hexane, and shake to see if they dissolve. B. Using clean test tubes, prepare the following set of nine systems: 3 test tubes, each containing 2 mL of 0.1 M KCl and 1 mL of hexane. 3 test tubes, each containing 2 mL of 0.1 M KBr and 1 mL of hexane. 3 test tubes, each containing 2 mL of 0.1 M KI and 1 mL of hexane. To study the reactivity of the halide salts, mix each of their solutions with 1 mL of aqueous solutions of Cl2, Br2, and I2. (Put 1 mL of Cl2 solution into a test tube with KCl solution, 1 mL of Cl2 solution into a test tube with KBr, and 1 mL of Cl2 solution into a test tube with KI solution. Then do the same for Br2 and I2 solutions.) It may be helpful to construct a table similar to the one shown below to record your observations. Each box in the table represents one of your nine test tubes. Cl - Br - I - Cl2 Cl2 + Cl - Cl2 + Br - Cl2 + I - Br2 Br2 + Cl - Br2 + Br - Br2 + I - I2 I2 + Cl - I2 + Br - I2 + I - Observe the color of the hexane layer after mixing, comparing it to the results in Part IIC. If the color is the same as would be expected for the added halogen, then no reaction has occurred. If it is not, then this is evidence of a reaction. <strong>VI</strong>-5
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VI-1 Chem 2115 Experiment # 6 PERIODIC RELATIONSHIPS

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