13 Synthesis of Tris(ethylenediamine)nickel(II) Chloride F18.pdf

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1| Synthesis of Tris(ethylenediamine)nickel(II) Chloride © 2018 MiraCosta Chemistry Dept. Synthesis of Tris(ethylenediamine)nickel(II) Chloride Objectives Carry out the synthesis of tris(ethylenediamine)nickel(II) chloride, and determine theoretical and percent yield. Background Tris(ethylenediamine)nickel(II) chloride is an ionic compound that includes a rather large polyatomic ion: [Ni(C 2 H 8 N 2 ) 3 ] 2+ . This polyatomic ion consists of one Ni 2+ ion with three ethylenediamine molecules, C 2 H 8 N 2 , bonded to it. (Ethylenediamine is often abbreviated “en”.) Because C 2 H 8 N 2 is a neutral molecule, the polyatomic ion resulting from the combination of one Ni 2+ and three C 2 H 8 N 2 molecules has an overall charge of 2+. The final ionic product of the reaction includes enough chloride anions (Cl ) to balance the 2+ charge on the cation. The correct formula for this compound is therefore [Ni(C 2 H 8 N 2 ) 3 ]Cl 2 . The three C 2 H 8 N 2 molecules bond to the central nickel ion using just their nitrogen atoms: Ethylenediamine = en = C 2 H 8 N 2 = H 2 C CH 2 H 2 N NH 2 This is simplified to: H 2 N NH 2 tris(ethylenediamine)nickel(II) chloride The balanced chemical equation for this reaction is: NiCl 2 · 6H 2 O(aq) + 3 C 2 H 8 N 2 (aq) [Ni(C 2 H 8 N 2 ) 3 ]Cl 2 (s) + 6 H 2 O(l) The procedure for synthesizing [Ni(C 2 H 8 N 2 ) 3 ]Cl 2 begins with making separate aqueous solutions of the two reactants, nickel(II) chloride hexahydrate (NiCl 2 · 6H 2 O) and ethylenediamine (C 2 H 8 N 2 ). The two solutions are mixed, and the mixture is put on ice to maximize precipitation of the solid product. Acetone is added to the product mixture to help with precipitation as well. Finally, the solid product is separated from the liquid using suction filtration. The amounts specified in the procedure will make NiCl 2 · 6H 2 O the limiting reactant, while the C 2 H 8 N 2 is used in an excess amount. (The · 6H 2 O in the formula of NiCl 2 · 6H 2 O indicates that in the crystalline structure there are six water molecules per every one NiCl 2 so be sure to include these when calculating the molar mass.) SAFETY: In this experiment you will be using acetone as one solvent, which is flammable, so there will be no flames in the lab during this experiment. Ethylenediamine is corrosive and toxic, so it will be stored in the fume hood to reduce the hazard of any spills. Nickel(II) chloride hexahydrate is toxic and an irritant. You must wear gloves when handling any of these compounds.
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Experimental Organic Chemistry: A Miniscale & Microscale Approach
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Gilbert/Martin
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