JOHNS HOPKINS UNIVERSITY Department of Chemistry AS.030.106 Introductory Chemistry Laboratory Spring 8. TRANSITION METAL CHEMISTRY PRE-LAB The pre-lab assignment ( PreLab 8 ) for this experiment is due Wednesday at 11:45 pm ET . Remember to login using your JH Uemail address (e.g. [email protected]). LAB QUIZ You should complete the lab quiz while watching the experimental video and before a±emp²ng the post-lab assignment. The quizzes are conducted in Blackboard and are due Saturday at 11:59 pm ET . You will have unlimited ²me to complete the quiz but only 1 a±empt at each ques²on. The quizzes are open note and you can collaborate (remember there is a difference between working together to solve problems and straight copying) with other members of the class. BLACKBOARD Blackboard has many resources that will help you be successful in this course. Some resources that will help you with this experiment include: ●Supplementary videos discussing the details of the experiment and analysis ●Sample data ●Prac²ce problems The bright colors of gemstones are generally due to the presence of transi²on metal compounds. You observed some of these colors in an early experiment during the first semester, when you started with a green [Ni(H 2 O) 6 ] 2+ coordina²on complex ion and made a violet [Ni(en) 3 ] 2+ coordina²on complex ion (with en as an abbrevia²on for the bidentate ligand, ethylenediamine). The complex ion, along with the anion that makes the neutral solid salt, is called the coordina²on complex. The anion (which is not shown in the figure above) is called the counter ion. Ligands are molecules or ions that act as Lewis bases (electron pair donors) and bond covalently (through a da±ve covalent bond) to the transi²on metal ion, producing a change in the electronic energy levels of the ion. This change in energy level changes the energy of light that is absorbed, giving the complex ion (and compound) a characteris²c color. The number of bonds made by the transi²on metal ion to the ligands is called the coordina²on number. In this experiment you will make cobalt coordina²on compounds containing different ligands. By comparing the results, you will be able to observe the effect of ligand field strength on the color of the compound. OBJECTIVES The objec²ves for this experiment include both laboratory skills and conceptual learning. ●Synthesize two transi²on metal complexes using laboratory skills you have learned in previous experiments. ●Use experimental techniques to speed up reac²ons. ●Use experimental techniques to maximize the produc²on of solid product. 1
JOHNS HOPKINS UNIVERSITY Department of Chemistry AS.030.106 Introductory Chemistry Laboratory Spring ●Use vacuum filtra²on to separate the solid product. ●Calculate yields of reac²ons based on reac²on stoichiometry. ●Understand the terminology of transi²on metal complexes, including ligands, complex ions, and counter ions. ●Use concepts from crystal field theory to explain the colors of transi²on metal complexes that you synthesize in the laboratory.