Lab 11 - Spectroscopic Determination of an Equilibrium Constant

 

determination of equilibrium constant lab report

Experiment 6: Determination of the Equilibrium Constant for Iron Thiocyanate Complex The data for this lab will be taken as a class to get one data set for the entire class. I. Introduction A. The Spectrophotometer Substances are colored when they absorb a particular wavelength of light in the visible region and transmit the other wavelengths. Experiment 3 Measurement of an Equilibrium Constant Introduction: Most chemical reactions (e.g., the “generic” A + B→ 2C) are reversible, meaning they have a forward reaction (A + B forming 2C) and a backward reaction (2C. For this equilibrium reaction, its ratio of products reactants is a constant. (2) K c is the equilibrium constant expression: (3) So K c for the iron(III) ion and thiocyanate ion is expressed as: (4) The value of K c will shift until equilibrium is reached, meaning any .


Determination of an Equilibrium Constant


A chemical reaction usually starts with reactants which react to yield products. Many times the reactants are completely used up to make products. However, the reactants sometimes do not completely turn into products. There is an equilibrium between the concentration of reactants and products.

At equilibrium, the reactants turn into product and the products decompose into reactants at the same rate. This ratio of the products to reactants at equilibrium is represented by the equilibrium constant, or K. K is found by taking the concentration and order of the products and dividing by the concentration and order of the reactants. First, a clean cuvette was obtained, rinsed, and filled three-fourths full with 0.

This was used as a the blank solution for determination of equilibrium constant lab report spectrophotometer, which was set at nm. Next, a mL volumetric flask was obtained and rinsed with distilled water. About 20 mL of 2. The volumetric flask was then filled with distilled water to the line on the neck. The cap was put onto the volumetric flask and it was agitated to ensure consistency of the solution.

This solution was then transferred into a clean, dry mL beaker. Next, about 20 mL of 1. The solution was then mixed with a glass stirring rod. A second clean, dry cuvette was filled three-fourths full with this solution using a disposable Pasteur pipet. The spectrophotometer was blanked with the cuvette filled with 0. Another 1. The cuvette used for measuring absorbance was filled with this solution using the disposable Pasteur pipet and was rinsed twice. It was finally filled three-fourth full with the solution in the mL beaker, determination of equilibrium constant lab report.

The spectrophotometer was blanked again with the 0, determination of equilibrium constant lab report. This process was repeated until For example using the first mixture, 1. For example using the mixture 1, Using the first mixture as an example. To find K, I took the concentration and order of the products and divided by the concentration and order of the reactants.

Finally, to find the average K, I added the 10 K values found and divided by My results do not seem very accurate. Even during the experiment, my partner and I agreed that our absorbance readings did not seem right. The readings jumped a significant amount between the first and second readings and the fourth and fifth readings. After the seventh reading, the absorbance readings seemed to be evening out, as the difference between readings was getting smaller.

When reading some of the absorbances, we took a second reading because a few times the absorbance reading was smaller than the previous. This did not seem right; the absorbance readings should have been going up determination of equilibrium constant lab report reading. Error may be attributed to the fact that a few drops of solution escaped the mL beaker during transfers between the cuvette. Error could have also resulted from the beakers not being totally clean, or the pipetment of solutions could have been inaccurate.

This would have caused the volumes and concentrations to be different than they actually were. Introduction A chemical reaction usually starts with reactants which react to yield products. Experimental First, a clean cuvette was obtained, rinsed, and filled three-fourths full with 0. Peter M. Paul J. Judith J. Mark F.

 

Determining an Equilibrium Constant Using Spectrophotometry — Adam Cap

 

determination of equilibrium constant lab report

 

You've just watched JoVE's introduction to spectrophotometric determination of the equilibrium constant. You should now understand the relationship defined by the Beer-Lambert law, how to determine concentration from absorbance using a spectrophotometer, and how to calculate an equilibrium constant using equilibrium concentrations. Determination of an Equilibrium Constant Introduction When chemical substances react, the reaction typically does not go to completion. Rather, the system goes to some intermediate state in which the rates of the forward and reverse reactions are equal. In this state, the reactants and the products have. c Exp. 5 - Determination of an Equilibrium Constant 1 _____University of Puget Sound Department of Chemistry Chem EXP. 5–DETERMINATION OF AN EQUILIBRIUM CONSTANT LABORATORY OBJECTIVES AND ASSESSMENTS 1. Understand the relationship between equilibrium constant and concentration.