determining of equllibrium constant

Topics: Chemistry, Potassium thiocyanate, Chemical equilibrium Pages: 2 (1133 words) Published: November 2, 2014

LAB REPORT 4 DETERMINING AN EQUILIBRIUM CONSTANT CAUSION
1. Potassium thiocyanate (KSCN) is hazardous
2. Wear protective material before performing the experiment. INTRODUCTION
This experiment outlines the techniques necessary to determine the equilibrium constant for the formation of an iron(III) thiocyanate complex ion (FeSCN2+) from Fe3+ and SCN- . The quantitative preparation of several solutions and subsequent measurement of the solution absorbance using a spectrophotometer are the techniques that will be used in this experiment. The absorbance measurement gives the concentration of FeSCN2+. The concentrations of Fe3+ and SCN- are obtained as the difference between the initial concentration and the concentration consumed by the formation of the FeSCN2+. The combined concentrations will be used to calculate an equilibrium constant for the formation of the complex. The reaction for the formation of the dark red FeSCN2+ complex ion is very simple OBJECTIVES.

The purpose of this lab is to experimentally determine the equilibrium constant, Kc, In this laboratory, we will determine the Equilibrium Constant for the reaction between the Ferric Ion (Fe3+) and the Thiocyanate Ion (SCN-) which produces Ferric Thiocyanate Ion (Fe(SCN)2+): Fe3+(aq) + SCN-(aq) Fe(SCN)2 (aq) MATERIALS

1. Cuvette 2. Pipet 3. Genesys 20 spectrophotometer 4. Dilute nitric acid, HNO3 5. Iron Nitrate, Fe(NO3)3 6 . Potassium thiocyanate, KSCN 7. Thermometer 8. Tissues 9.Protective devices PROCEDURE OR METHODS

In Part A of the lab, I prepared six solutions – including a reference solution (known concentration) and a series of five test solutions (varied in concentration of SCN– (aq)). In Part B of the lab, I measured the absorbance of the solutions using a Spec 20. After collecting the data, I calculated the unknown equilibrium concentrations of the FeSCN2+...
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