Redox Activity Series Lab

An Activity Series АР Chemistry Laboratory lntroduction Iп this expctimcnt, а series of metals and а seгies of noпmetal halogens аге studied to find tl1eir relative reactivities. The reactivity of the meta!s is determined Ьу comЬining the metals with а complemen­ tary series of metal ions in solution. The гeactivity of thгee halogens is found Ьу mixiпg each with а l1alide ion solutioп. Using the observed reactions, an activity series, fгom most reactive to least reactive, is developed for tl1e metals and for the halogens. Concepts • Oxidation-гeduction • Activity seгies • Half-cell гeaction Background А гanking of elements according to their гeactivity is called an activity series. Fог example, an activity seгies containing the elements calcium, gold, and iron would рнt the reactive calcium at the top, iron in t!1e middle; and the unreactive gold at the bottom. If а piece of iron metal is placed in а solution of gold nitгate, the iгon dissolves forming positive ions in solution while solid gold metal appears. The тоге reactive metal (iгon) displaces ions of the less reactive metal [gold(III)] from solution. The less reactive element appears as the solid element. Re3:ctions such as these аге examples of oxidation-reduction reactions. Oxidation is defined as the process of losing electrons and substances tl1at lose electrons during chemical гeactions are said to Ье oxidized. Substances that gain electrons duгing chemical reactions undergo reduction and are said to Ье гeduced. If one reactant gains electrons, anotheг must lose electгons. Oxidation and reduc­ tion reactions occur simultaneously, and there must Ье an equal number of electrons lost апd gained during the two reactioпs. In the reaction of iroп metal with gold ions, the iгon metal is oxidized and the gold ions are reduced. The more reactive metal is the one that is more easily oxidized. ЗFe(s) --э- 3Fe2+(aq) + 6e- 2Au3+(aq) + бе- --э- 2Au(s) Iron loses electrons. Oxidation Gold gains electrons. Reduction ЗFe(s) + 2Au3+(aq) - 3Fe2\aq) + Au(s) Oxidation-reduction Figure 1. Reduction of gold ions Ьу iron metal. Wheп writing oxidatioп-reduction reactions, it is customary to break фе reaction into the two parts ог half-cell гeactions. These half-cell reactions represent the separate oxidation and reduction pro­ cesses that оссuг simultaneously. The electrons within the two half-cell reactions must Ье equal so there is по net gain ог loss of electrons fог the oveгall reaction. When а substance readily loses electrons (and is oxidized), it acts as а good reducing agent. When а substance has а st.rong tendency to gain electrons (and Ье гeduced), it acts as а good oxidizing agent. Gold ions, Au3 +(aq), have а stгong tendency to acquire electгons to foгm пeutгal gold atoms, Au(s). Gold ions аге thus easily reduced and act as good oxidizing agents. Experiment Overview The puгpose of Lhis expeгiment is to deteпnine the activity seгies for five metals and fог tl1гee halo­ gens. The fiгst рагt of this experiment derives an activity series for metals and uses а microscale teclшique. The second рагt deгives ап activity series fог halogens. lt makes use of а solvent extгac­ tioп teclшique. The seгies of melals to Ье stlldied are соррег, ziпc, magпesium, lead, апd silveг. Solutions of metal nitгates for eacl1 of tl1ese metals аге placed iп гeaction wells. А piece of each metal is then placed in tl1e otl1eг metals' nitгate solutions and obseгved to see if any гeaction occurs. If а metal гeacts with anotl1eг meLal nitrate, then tl1e solid metal has redнced the otl1eг metal ion and is, t!1егеfоге, tl1e тоге reactive meta! of the two. Ву compai-ing the results of 16 diffeгent reactions, t!1e five met­ als аге гanked from most reactive to least гeactive. In Part 2, tests аге performed to determine the activity seгies of the haloge11s. Chlorine (Cl2), bгo­ mine (Вг2), a11d iodine (I2 ) are placed in solutions containing chloride (Cl-), bromide (Вг-), ог iodide (I-). An activity seгies of the 11onmetallic halogens places the most гeactive halogen at the top. In the reaction of а free halogen (Х2) with а diffeгent halide ions (У-), the fгее halogen gains electгons and is theп гeduced to its coпesponding halide ions (Х-). The original halide ions lose electrons and theгefore are oxidized to their coпesponding fгее halogen (У2). Tl1e more reactive halogens displaces io11s of the less гeactive halides from solution. l11 an activity series of halogens, the most reactive halogen is the one most easily'reduced. X2(aq) + 2e-(aq) - 2x-(aq) Reduction 2Y-(aq) - Yl(aq) + 2е- Oxidation Oxidation-reduction Figure 2. Reduction of а free halogen Х2 Ьу halide ions у _То determine if а reaction occurs, а method is needed to identify which halogen is pгesent. Halogens dissolve in the nonpolar solvent mineral oil foгming diffeгent coloгed solutions. Mineral oil does not dissolve in water, but when shaken with an aqueous halogen solution, the halogen is extracted froщ the water into the mineгal oil. The color of the mineral oil layer indicates which hal­ ogen is present. Materials Copper foil, 6 х 6 mm pieces, 4 Magnesium nitrate solution, Mg(NO3)2, 0.1 М, 4 mL Zinc foil, Zn, 6 х 6 mm pieces, 4 Lead nitrate solution, Pb(NO3)2, 0.1 М, 4 mL Magnesium ribbon, Mg, 6-mm pieces, 4 Lead foil, РЬ, 6 х 6 mm pieces, 4 24-well reaction plate Beral-type pipets, 5 Silveг nitrate solution, AgNOз, 0.1 М, 4 mL F0гceps Сорреr(П) nitгate solнtion, Cu(NO3)2, 0.1 М, 4 mL Stirriпg rod Ziпc пitrate solнLion, Zn(NOз)2, 0.1 М, 4 mL Procedure Port I " Deterrníne an Actívíty $eríes fcr Metols. of white paper so that there are 6 wells across (columns) and 4 wells down (rows). Refer to Figure 3 to see how the weils are anangecl. Note that each well is identihed by an unique combination of a letter and a number, where the letter refers to a horizontal row and the number to a vertical column. 1. Place the Z|-well plate on top of 2. Put one dropper-full (about a piece 15 drops or 1 mL) of copper(Il) nitrate solution in wells B I , C I , and D1 in the first column. 3. Putonedropper-fullofmagnesiumnitratesolutioninwells A2,C2,andD2of thesecondcolumn. 4. Put one dropper-full of lead nitrate solution in wells 43, 83, and D3 of the third column. 5. Put one dropper-full of zinc nitrate solution in wells A4,B4,and C4 of the fourth colurnn. 6. Put one clropper-full of silver nitrate solution in each of the wells A5 through D5 in the fifth column. 7. Put a small piece of copper metal in each of the wells containing a solution in the first row. B. Add-magnesium metal to the solutions in the second row, add lead metal to the solutions in the third row, and add zinc metal to the solutions in the fourth row. Use a stining rod to submetge each metal in the solutions. Allow to stand at least 5 minutes. 9. Determine if a reaction has occurred in each well by observing if if the surface of the metal has become coated. a new metal has deposited Record each observation as either coating forms or no reaction in the Part r23456 A Row A Row B Row C Row D Figure 3. I Data Table or