Analysis Of The Beer-Lambert Law For Kmno4
Introduction Objectives Validate the Beer-Lambert law for KMnO4. To determine the pKa for an acid-base indicator To estimate the equilibrium constant for the formation of complex ion Fe(NSC)²ꭞ The function of part two of the experiment is to find the value of the constant K, in the following equilibrium constant: K=[Fe (NSC) ²⁺]/ [Feᶟ⁺] [NCS⁻], while not disrupting the equilibrium.
Theory
For part one. The majority of chemical compounds are known to absorb UV or visible light. Depending on the nature of the electronic transitions involved determine the wavelengths absorbed. The concentration of the compound present in a sample determine the intensity of light absorbed. Many compounds absorb very strongly we can therefore monitor …show more content…
Starting with a 4X10⁻⁴M KMNO₄ stock solution, dilute the stock to prepare the following four solutions using clean, dry test tubes:
4x10⁻⁴M, 2x10⁻⁴M, 1x10⁻⁴M and 0.5x10⁻⁴M and measure the absorbance of each solution, respectively. Use a spectrometer to determine the absorbance of each sample. Cuvettes are placed in the cells. Rinse the cuvette with deionised water and then with the solution it will contain to avoid experimental error and an inaccurate reading of the absorbance. Fill cuvette to approx. 3/4. Be sure to adjust the machine to zero absorption. Note that KMnO4 has maximum at a wavelength of 524nm, a baseline test using deionised water is run for wavelengths in the range 500nm-550nm. Start with the most dilute samples placing water in the first cell and add samples anticlockwise in order of increasing concentration. Ensure all axes are labelled, graph has a title and note the units. Once results are obtained, plot a graph with concentration on the x-axis and absorbance on the y-axis (absorbance vs concentration).
Determine the concertation of the unknown solution provided using your …show more content…
Incorrect decontaminant procedure for cuvette: not washing with deionised water and then the solution it will contain.
While all the results did not verify the Beer- Lambert law, there is correlation between the results for the absorbance for 4x10⁻⁴ of Potassium Permanganate which is .931 and 2x10⁻⁴ which is .427. We can see evidence of the Beer – Lambert law, as the difference between the two absorbance values is 0.5063, which is approximately 1/2, which are expected results.
These errors also apply to part two of the experiment: Determination of the Equilibrium Constant of [Fe (NCS)] ²⁺ as the absorbance values for [Fe (NCS)] ²⁺ are also not obeying the beer- lambert law. This means that for future experimentation, techniques of accuracy and precision must be applied strictly and carefully, to ensure results are represented as accurately as possible, with minimum experimental error. It is clear that the errors in this experiment are systematic, as errors are consistent and the procedure was wrongly carried out by the experimenters.
Theory
For part one. The majority of chemical compounds are known to absorb UV or visible light. Depending on the nature of the electronic transitions involved determine the wavelengths absorbed. The concentration of the compound present in a sample determine the intensity of light absorbed. Many compounds absorb very strongly we can therefore monitor …show more content…
Starting with a 4X10⁻⁴M KMNO₄ stock solution, dilute the stock to prepare the following four solutions using clean, dry test tubes:
4x10⁻⁴M, 2x10⁻⁴M, 1x10⁻⁴M and 0.5x10⁻⁴M and measure the absorbance of each solution, respectively. Use a spectrometer to determine the absorbance of each sample. Cuvettes are placed in the cells. Rinse the cuvette with deionised water and then with the solution it will contain to avoid experimental error and an inaccurate reading of the absorbance. Fill cuvette to approx. 3/4. Be sure to adjust the machine to zero absorption. Note that KMnO4 has maximum at a wavelength of 524nm, a baseline test using deionised water is run for wavelengths in the range 500nm-550nm. Start with the most dilute samples placing water in the first cell and add samples anticlockwise in order of increasing concentration. Ensure all axes are labelled, graph has a title and note the units. Once results are obtained, plot a graph with concentration on the x-axis and absorbance on the y-axis (absorbance vs concentration).
Determine the concertation of the unknown solution provided using your …show more content…
Incorrect decontaminant procedure for cuvette: not washing with deionised water and then the solution it will contain.
While all the results did not verify the Beer- Lambert law, there is correlation between the results for the absorbance for 4x10⁻⁴ of Potassium Permanganate which is .931 and 2x10⁻⁴ which is .427. We can see evidence of the Beer – Lambert law, as the difference between the two absorbance values is 0.5063, which is approximately 1/2, which are expected results.
These errors also apply to part two of the experiment: Determination of the Equilibrium Constant of [Fe (NCS)] ²⁺ as the absorbance values for [Fe (NCS)] ²⁺ are also not obeying the beer- lambert law. This means that for future experimentation, techniques of accuracy and precision must be applied strictly and carefully, to ensure results are represented as accurately as possible, with minimum experimental error. It is clear that the errors in this experiment are systematic, as errors are consistent and the procedure was wrongly carried out by the experimenters.