Chemical Equilibrium in Solution Essay

947 Words Feb 1st, 2013 4 Pages
Chemical Equilibrium in Solution

2/5/13 Jim Jacobs (Partner: Jessica Janiga)

The purpose of this experiment was to determine the equilibrium established between iodine species [I3-, I2, and I-] dissolved in an aqueous KI solution. The values obtained for equilibrium were as follows: Kc (run#1) = 620; Kc (run#2) = 599; Kc (run#3) = 545. In effort to distinguish between the species of iodine the distribution coefficient ratio between two immiscible solvents (dichloromethane and water) was determined at multiple concentrations.

I. Introduction

The purpose of this experiment is to determine the equilibrium constant of iodine species at various concentrations. The equilibrium equation of the iodine
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It is also necessary that these titrations occur when iodine is at stable equilibrium between the aqueous and organic layer so an accurate estimation of the distribution can be made. The establishment of k at certain equilibrations of water and dichloromethane can then be used to determine the concentrations of the other species by solving for molecular iodine in the following equations:

I3-=T- I2 and I-=C- I3-

Where T represents the total iodine concentration ([I3-] + [I2] + [I-]) in aqueous layer and C represents the initial concentration of KI in the aqueous layer.

II. Experimental Method

The experimental method was similar to that described in Experiment 12 from the textbook (Garland, Nibler, and Shoemaker, 8th ed., Exp. 12). The procedure was modified as follows: Dichloromethane was used as the organic solvent in place of carbon tetrachloride. No thermal bath was employed to aid in reaching equilibrium. The 500 mL flasks were not placed in a battery jar containing water at 25°C after reaching equilibrium. No second sample was used. Soluble starch solution was used in place of Thyodene. Each solution was titrated with sodium thiosulfate with the volume of sodium thiosulfate added by:

VTOTAL = VFINAL - VINITIAL Where V symbolizes volume. The following table is indicative of the amounts utilized in the experiment:

III. Results

The results of the titrations of runs 1-3 along the

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