In this experiment, the concentration of an unknown permanganate solution will be determined. Spectroscopic techniques will be used to measure various known concentrations of permanganate solutions to create a calibration curve for the absorbance of light vs. the concentration and will be used to determine the unknown concentration1.
Introduction
In order to perform this experiment, proficiency with using spectrometers, burettes, volumetric flasks, weighing by difference, and making a hot-water bath are essential1.
By using a spectrometer’s function to analyze the absorbance of light of each of the known solutions, the resulting linear correlation will provide an equation similar to the Beer’s Law equation required for calculations1.
The linear
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Procedure
1. Obtained required materials and prepared necessary setup to complete the experiment.
2. Prepared unknown solution by using a hot-water bath to heat the 100mL volumetric flask containing 35mL of the unknown Mn2+ solution, 5mL of the provided phosphoric acid and between 0.3 to 0.5g of potassium periodate1.
3. While the unknown solution was being made, five cuvettes were prepared, one containing distilled water to calibrate the spectrometer and the other four, separately containing one of the four known permanganate solutions1.
4. After calibration, the most concentrated (known) solution was used to obtain max. The significance of this step is to set the spectrometer to measure at that particular wavelength1.
5. Manipulated with settings on the program to display a graph showing absorbance vs. concentration. Collected absorbance data for the three remaining known solutions to obtain a linear fit1.
6. Returned to the unknown cooked solution and collected absorbance data for the solution using a cuvette. Recorded results and used mathematics to ultimately determine the concentration of the unknown
With these absorbance numbers a concentration curve was constructed and the unknown solution was determined by finding the point of absorbance on the curve.
10 microliters of the sample is then added and the assay absorption is measured at 340nm. If absorbance was above 1.5, samples were diluted.
The ending result of this experiment confirms that as five test tubes are lined up with the varying level of absorbance, different results in the level of absorbance will appear as well, this is visible in above table. Thus, this is due to the varying amount of water in the solution. The blank sample had a 0.30 in its level of absorbance.
Time) because it had a correlation closest to 1. All three orders were graphed and a linear regression was used to see which graphed order was closest to 1. The order was determined by comparing the concentration and time to the mathematical predictions made using the integrated rate laws. Analyzing each graph and finding each correlation helped determine which graph was closest to 1. The more concentrated a solution is, the higher the absorbance of that solution. This is due to Beer’s Law. The law measures the absorbance of a solution by determining how much light passes through a solution. As the concentration of a solution increases, fewer wavelengths of light are able to pass through the concentrated solution. The absorbance at 60 seconds was 0.573 (Figure 1: Table1). To calculate the concentration (molarity), the Beer’s Law equation was used, Abs = slope(m)+b. Plugging in what is known into the Beer’s Law equation resulted in 0.573 = 3.172e+004 + 0, where the concentration is determined by M = 0.573-0/ 3.172e+004. So, the concentration at 60 seconds using the equation (M = 0.573-0 / 3.172e+004) was 1.824e-5 M. The 1st order graph resulted in k=0.006152 (Figure 1: Graph 1). Other groups also resulted in their decolorization of CV to be the 1st rate
The Beers Law calibration experiment used many concentrations of crystal violet solutions. Each of these solutions were test and analyzed in order to determine the absorbance of each concentration The results were than graphed and produced a slope of 1.00E05 with an intercept of -2.21E-02.
Each stock solution was placed in a colorimeter and was tested for it Absorbance. A computer program tested and drew up the Calibration curve/linear fit equation. However, the computer could not protect potential errors. An error for determining the concentration of the diluted and undiluted, could be a skew linear fit equation. The linear fit equation could be skewed by having an inadequate ratio of the stock solution and distilled water. For example, when making stock solution 1, 0.021(L) was used instead of 0.020(L) can throw the calibration curve, resulting a skewed linear fit equation. If the “blank” was not fully clean or had left over Allura Red residue, then the “blank” was tampered with. A tampered “blank” means any comparisons with it would have a wrong Absorbance reading. However, the most likely and most effective error, is calculation. Using the wrong V1 and V2 to determine the concentration of the undiluted would affect the answer of the grams Allura Red would be consume and the amount of molecules of Allura Red. The colorimeter is adjusted to a wavelength of 470 nm is maximize the absorbance of the Allura Red. If wavelength was place at 565 nm, then Allura Red would not absorb as much color of
The dark, navy blue colored graph represented the absorbance curve for the S1 sample. The red colored graph represented the absorbance curve for the S2 sample. The green colored graph represented the absorbance curve for the P1 sample. The purple colored graph represented the absorbance curve for the P2 sample. The gaps between the P2 curve was due to the oversaturation that led to the inconclusive spectrophotometer readings. The blue colored graph represented the absorbance curve for the P1 low salt sample. The orange colored graph represented the absorbance curve for the P2 low salt sample. The light blue colored graph represented the absorbance curve for the P1 medium salt sample. The light pink colored graph represented the absorbance curve for the P2 medium salt sample. The light green colored graph represented the absorbance curve for the P1 high salt sample. The light purple colored graph represented the absorbance curve for the P2 high salt
b. Describe the spectral curve of each target type with respect to its absorption and reflectance characteristics. (3)
3. The spectrophotometer was set at 420nm. Distilled water was also used as the ‘blank’.
The absorbance obtained from the results of each test sample, then put into the equation of calibration curve in accordance with the respective raw substances, after which it would have obtained the value of molar absorptivitas. The molar absorptivitas results obtained are used in the determination of the percentage of the sample levels
In the table below, we have the absorbances we collected using the spectrometer. We have the absorbances of the color dyes, the color dyes diluted, and our given solution.
Absorbance can also be found using Equation 4 as well, for this specific formula you plug the percent transmittance directly in the equation instead of changing it to transmittance. A calibration curve (Figure 1) was created with the data from Table 1. A calibration curve for this experiment helps find the actual concentration of the made and unknown solutions. The absorbance is on
Incorporation of assay controls included setting up a spectrophotomer and running the chart recorder with a full-scale deflection before the start of the assay. The set recorder had a corresponding value of 1 for the change in the absorbance. Therefore, prior testing was done to observe whether a change occurred in the readings. This helped to indicate that the results were valid, as they could have been affected by a fault during the setting up of the spectrophotometer. On the other hand this was considered as one of the controls for the experiment. Nevertheless, a new cuvette had to be used for each assay.
In this lab the concentration of allura red will be found. The vernier colorimeter will be used for this lab. Stock solution of a known concentration will be made, the absorption of each will be measured, when absorbance vs. concentration is plotted it should result in linear plot, which is called a calibration plot. The plot comes from the beer-lambert law, which is A=Kc. Measuring the concentration of allura red can be found by measuring the absorption of light through the solution. Cuvettes will be used in this lab to find concentration each solution; they will be placed in the cuvette then put into colorimeter to find absorption. Once that is complete data pairs will be examined by making a graph of absorbance vs. concentration with a
This was done by using SpectroVis and graphical analysis during and after the lab. The lab began by creating a dilute stock solution known as C. This was done by mixing stock solution in a serological pipet and diluting it with DI water. Proceeding this step, solution C was carefully poured into a cuvette followed by solutions A, B, D, E, and nondiluted stock that were obtained from other groups. After all the solutions were obtained, including an additional a cuvette of DI water, the SpectroVis was calibrated. This was done using DI water and was in order to select the correct wavelength, which was determined to be 529 nm. Then after the SpectroVis was calibrated, the nondiluted stock solution was put in the SpectroVis and the data began to be collected. Solutions A-E were then put in the SpectroVis and their absorbance was collected. Finally the unknown cuvette was put in the SpectroVis and its absorbance was recorded which concluded creating the calibration curve. After this then the SpectroVis was reset and a cuvette of sodium hydroxide was put in the SpectroVis for about 16 minutes. Following the completion of this step that portion of the lab was complete. After the lab was cleaned up and all the data was obtained, the data was then put into excel to make 4 different graphs, absorbance vs. concentration, absorbance vs. time, ln absorbance vs time, and 1/absorbance vs time. These graphs were used in order to find their slope which allowed to help find x and k. By using x, k, and the data obtained the rate law was able to be determined. By finding the rate law the purpose of the lab was