Lab Report 1 (Spectrophotometric Determination of the Stability Constant of a Complex Ion) - Experiment 1 Experiment Title Spectrophotometric

Lab Report 1 (Spectrophotometric Determination of the Stability Constant of a Complex Ion)

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Experiment # 1 Experiment Title: Spectrophotometric Determination of the Stability Constant of a Complex Ion Student Name: Lab Partner: Student Number: Section Number: 0116 Date the experiment was performed: Jan/17 th /2013 Date the lab report was submitted: Jan/24 th /2013 Submitted to Tae hun Kim Pre-lab /15 Purpose /5 Experimental Method /5 Collection of Data /4 Results and Calculations /25 Accuracy /5 Summary /4 References /2 Experimental Technique /10 Report Presentation /10 Writing 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 H 2 O, NH 3 , 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) thiocyanate Fe(SCN) 2+ using spectrophotometry; the formation of the ion is the product of the following reaction with iron (III) ion Fe 3+ and thiocyanate ion SCN - as reactants : [Fe(H 2 0) 6 ] +3 (aq) + SCN - (aq) [Fe(H 2 0) 5 (SCN)] +2 (aq) + H 2 O Since 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 as K= 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.

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