Spectrophotometric Determination of the Equilibrium Constant of a Reaction
Date Performed: January 10 & 15, 2013
Spectrophotometric Determination of the Equilibrium Constant of a Reaction
R.J.V. Ortega and J.C.V. Gatdula
Institute of Chemistry, College of Science
University of the Philippines, Diliman, Quezon City, Philippines
Received January 22, 2013
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ABSTRACT
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------------------------------------------------- The experiment is conducted in order to determine the equilibrium constant of the Iron (III) – Thiocyanate System through the use of a UV-Vis Spectrophotometer. It is achieved by inserting a series of solutions with varying concentrations of Fe3+ and SCN- into a cuvette, then to the spectrophotometer in order to determine the degree of absorbance of the [FeSCN2+].First, standards solutions are used in order to determine several critical values. Then, unknown solutions are used in order to determine their equilibrium constant. Results from the experiment showed that the average equilibrium constant of the reaction in the unknown solutions is479.27, which gave a 54.22% difference with the literature value of 1047.Although there is a high percentage of error, the spectrophotometer may prove to be a successful tool in determining the equilibrium constant of a given reaction.
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Introduction
Chemical equilibrium is defined as the moment when two opposing forces in a chemical reaction, the forward and the reverse reactions, occur at the same time or at equal rates. It is what all chemical systems try to achieve, considering other stresses and changes that might occur or affect the system. The rate at which the chemical equilibrium is achieved is called the equilibrium constant, denoted by Keq. It is affected mostly by temperature. Given a chemical equation:
Spectrophotometric Determination of the Equilibrium Constant of a Reaction
R.J.V. Ortega and J.C.V. Gatdula
Institute of Chemistry, College of Science
University of the Philippines, Diliman, Quezon City, Philippines
Received January 22, 2013
-------------------------------------------------
-------------------------------------------------
-------------------------------------------------
ABSTRACT
-------------------------------------------------
------------------------------------------------- The experiment is conducted in order to determine the equilibrium constant of the Iron (III) – Thiocyanate System through the use of a UV-Vis Spectrophotometer. It is achieved by inserting a series of solutions with varying concentrations of Fe3+ and SCN- into a cuvette, then to the spectrophotometer in order to determine the degree of absorbance of the [FeSCN2+].First, standards solutions are used in order to determine several critical values. Then, unknown solutions are used in order to determine their equilibrium constant. Results from the experiment showed that the average equilibrium constant of the reaction in the unknown solutions is479.27, which gave a 54.22% difference with the literature value of 1047.Although there is a high percentage of error, the spectrophotometer may prove to be a successful tool in determining the equilibrium constant of a given reaction.
-------------------------------------------------
Introduction
Chemical equilibrium is defined as the moment when two opposing forces in a chemical reaction, the forward and the reverse reactions, occur at the same time or at equal rates. It is what all chemical systems try to achieve, considering other stresses and changes that might occur or affect the system. The rate at which the chemical equilibrium is achieved is called the equilibrium constant, denoted by Keq. It is affected mostly by temperature. Given a chemical equation: