ADVANCED AP PLACEMENT CHEMISTRY Introduction Activity Series An activity series of metals is a table of metals arranged in the order of their decreasing chemical activity or the ease at which the metal will give up one or more electrons to form positive ions. This table is similar to the electrochemical series of elements. For example if you take the group of metals magnesium, mercury and nickel, magnesium is the most reactive and mercury the least. To empirically determine which of these metals is more reactive, place a piece of the metal in a salt solution of the other. The more reactive metal will replace the less reactive metal and the less reactive will appear in the solid form. The reactive metal has been oxidized, the less reactive metal has been reduced. A similar series can be constructed from nonmetallic halogens. The most active halogen is the most easily reduced, accepting electrons from the less active species and replacing it in the halide. Oxidation and reduction reactions occur concurrently therefore the number of electrons lost must equal the number of electrons gained. A good reducing agent easily gives up it electrons and is oxidized. Likewise, a good oxidizing agent has a strong tendency to acquire electrons and is reduced. Objective In these experiments, an activity series for a group of metals and a group of non-metals will be determined empirically. Chemicals and Equipment Materials included in this kit: 15 strips Magnesium metal 15 strips Copper metal
15 strips Lead metal 60 pieces Zinc metal 3 50mL Copper Nitrate, 0.1M 3 50mL Magnesium Nitrate, 0.1M 3 50mL Zinc Nitrate, 0.1M 3 50mL Lead Nitrate, 0.1M 1 100mL Bromine Water 1 100mL Chlorine Water 1 100mL Iodine Water 2 50mL Sodium Bromide, 0.1M 2 50mL Sodium Chloride, 0.1M 2 50mL Potassium Iodide, 0.1M 2 100ml Mineral Oil 1 set Student study and analysis copy masters 1 Teacher Guide Materials required but not included: 15 each 24 well microtiter plates 180 each 13 100 test tubes with stoppers Safety equipment required: Rubber gloves Apron Safety goggles Safety Note: Lead compounds are very poisonous. Chlorine water, Bromine water and Iodine water give off irritating fumes and are poisonous by ingestion. Use extreme care when handling these compounds. Wash your hand thoroughly. Procedure Activity Series of Selected Metals 1.) Set up a 4 4 analysis matrix in the microtiter plate by placing 1 ml (15 drops) of each of the nitrate solutions on the following wells: Copper nitrate - wells 2-4 of column 1 Lead nitrate - wells 1, 3 & 4 of column 2 Zinc nitrate - wells 1,2 & 4 of column 3 Magnesium Nitrate - wells 1, 2 & 3 of column 4 2.) Place a small piece of copper in each of the wells of the first row containing a solution. Add a lead piece to the solutions of the second row, zinc pieces to the third row and magnesium pieces to the forth row.
Cu Pb Zn Mg Cu 2+ Pb 2+ Zn 2+ Mg 2+ Analysis Matrix 3.) Allow the plate to stand at least 5 minutes. Determine if a reaction has occurred in the wells by looking for a chemical deposit on the metal or a precipitate in the bottom of the well. Record your data and determine for each well which metal was more reactive. Activity series of selected halogens. 1.) Halogens, Cl 2, Br 2 and I 2 are soluble in nonpolar solvents such as mineral oil. The presence of a halogen will be determined by the color it exhibits in mineral oil. To determine the colors, place 1mL (15 drops) of Chlorine water, Bromine water and Iodine water in 3 separate test tubes. Add 1mL of mineral oil to each test tube stopper and shake for 15 seconds. Place the test tubes in a test tube rack and allow the mineral oil and water to separate. Record the color of the mineral oil layer (upper layer) for each halogen.
2.) Determine if the halide ions impart color to mineral oil by repeating step 1.) with 1mL each of the solutions of NaCl, KI and NaBr. Record your results. 3.) Set up a 3 3 analysis matrix similar to the one used is the first experiment using test tubes. Place 1mL of the solution of NaCl in to each of two test tubes. Do the same for the solutions of KI and NaBr. To the NaCl test tubes add 1mL of Bromine water in one and 1mL of Iodine water in the other. To the KI test tubes add Chlorine water and Bromine water and to the NaBr test tubes add Iodine water and Chlorine water. Add 1mL of mineral to each test tube, stopper all of the test tubes and shake for 15 seconds. Allow the layers to separate and record the colors for the mineral oil layer in each test tube. NaCl NaBr KI Cl 2 water Br 2 water I 2 water Analysis Matrix
Chemical disposal: Collect the solutions for each experiment and keep separate. Dispose of these solutions in accordance with local regulations. Discussion and Laboratory Report (1) In your lab report include balanced net ionic equations for all reactions that occurred with the metals. List the metals in decreasing ease of oxidation (activity series) and compare to an activity series found in your textbook. (2) Write reduction half reactions for each metal ion and arrange the list in order of decreasing ease of reduction. Compare your list to a table of reduction potentials found in your textbook or the CRC Handbook of Chemistry and Physics. (3) Describe what occurs when halogen and halide ions are extracted by a nonpolar solvent such as mineral oil. (4) Write balanced net ionic equations for the reactions which occurred with the halogens. List the halogens in decreasing order of reactivity. Compare your list to an activity series in your textbook. (5) Write reduction half reactions for each of the halogens. Arrange in order of decreasing ease of reduction. Compare the list to the table of reduction potentials as in step (2) above.