Background Ni\(^{2+}\) in aqueous solution exists as the octahedral complex ion hexaaquanickel (II), [Ni(H\(_2\)O)\(_6\)]\(^{2+}\). When the bidentate ethylenediamine ligand ( en ) is added to the solution in a 1:1 concentration ratio, it replaces two water ligands of the [Ni(H\(_2\)O)\(_6\)]\(^{2+}\) to form [Ni(H\(_2\)O)\(_4\)(en)]\(^{2+}\): Further additions of ethylenediamine form the di- and tri- ethylenediamine complex, which have geometric and/or optical isomers. Answers: Bidentate isomers: Tridentate isomer: Materials: 2 mL of 1.0 M Nickel sulfate (NiSO\(_4\)) solution 3 mL of 2.0 M Ethylenediamine (H\(_2\)NCH\(_2\)CH\(_2\)NH\(_2\)) solution 125 mL Erlenmeyer flask Four small test tubes (and a small beaker to hold them Safety Ethylenediamine is a caustic, flammable liquid with an irritating vapor similar to ammonia. Nickel sulfate is a suspected carcinogen. Procedure: Add 2 mL of nickel sulfate solution to the 125 mL Erlenmeyer flask. Bring up to 30 mL with water. Calculate the final concentration of nickel (II) ion. Transfer about 1 mL into a test tube. Add to the Erlenmeyer flask 1.0 mL of ethylenediamine solution. Record your observations. Transfer about 1 mL into a clean test tube. Add another 1.0 mL aliquot* of ethylenediamine solution to the Erlenmeyer flask. Record your observations. Transfer about 1 mL into a clean test tube. (aliquot = a volume of a solution) Add another 1.0 mL of ethylenediamine into the Erlenmeyer flask. Record your observations. Transfer about 1 mL into a clean test tube. Group test tubes together to contrast the four colors. Optional: Work in teams to obtain the spectrum of each solution by UV-VIS spectroscopy. Clean-Up: Collect all waste in the designated container. Discussion: Draw the missing isomers in the Background section and describe in each case the type of isomerism. At approximately what wavelengths of the electromagnetic spectrum do these complexes, [Ni(H\(_2\)O)\(_6\)]\(^{2+}\), [Ni(H\(_2\)O)\(_4\)(en)]\(^{2+}\), [Ni(H\(_2\)O)\(_2\)(en)\(_2\)]\(^{2+}\), [Ni (en)\(_3\)]\(^{2+}\), absorb light? Use your understanding of the splitting of d orbitals and the spectrochemical series to explain your results.