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Experiment # 1Experiment Title: Spectrophotometric Determination of the StabilityConstant of a Complex IonStudent Name: Lab Partner:Student Number: Section Number: 0116Date the experiment was performed: Jan/17th/2013Date the lab report was submitted: Jan/24th/2013Submitted to Tae hun KimPre-lab/15Purpose/5Experimental Method/5Collection of Data/4Results and Calculations/25Accuracy/5Summary/4References/2Experimental Technique/10Report Presentation/10Writing Initiative/15
Introduction:When a metal ion acting as a Lewis acid, reacts with a ligand the species formed is called a complex ion. Some common ligands are H2O, NH3, Cl-and heavier halides. Many of these complex ions are expressed by the equilibrium constant for the formation of the complex ion. Such equilibrium constants are referred to as stability constants or formation constants. In this experiment an aqueous solution of ferric ions is reacted with thiocyanate ion to form a complex ion. Purpose:The purpose of this experiment is to determine the equilibrium constant for the formation of the complex ion iron (III) thiocyanateFe(SCN)2+ using spectrophotometry; the formation of the ion is the product of the following reaction with iron (III) ion Fe3+and thiocyanate ion SCN-as reactants : [Fe(H20)6]+3(aq) + SCN-(aq) [Fe(H20)5(SCN)]+2(aq) + H2OSince the concentration of water in dilute aqueous solution is constant, water is omitted from the equation to a simplified version:Fe+3(aq) + SCN-(aq) Fe(SCN)+2(aq)The stability constant for this experiment is expressed asK= Fe(SCN)+2(aq)[Fe+3(aq)] [SCN-(aq)]
Experimental Method:Part A:1.The spectrophotometer was turned on by following instructions that were given on the lab bench. 2.Six test tubes were labelled from 0-5.3.The solutions were prepared as described in Table1. of the CHM 120 Course Manual on page 22. 4.After the solutions were prepared each test tube was sealed with a small square Parafilm and mixed thoroughly.